document.write( "Question 103929: The sum of two numbers is 27. one half of the first number plus one third of the second number is 11. Find the numbers \n" ); document.write( "
Algebra.Com's Answer #75611 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Translate the word problem into a system of equations\r
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\n" ); document.write( "\n" ); document.write( "\"x%2By=27\" \"The sum of two numbers is 27\"
\n" ); document.write( "\"%281%2F2%29x%2B%281%2F3%29y=11\" \"one half of the first number plus one third of the second number is 11\"\r
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Solved by pluggable solver: Solving a linear system of equations by subsitution

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\n" ); document.write( " \"%281%2F2%29%2Ax%2B%281%2F3%29%2Ay=11\" Start with the second equation
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\n" ); document.write( " \"6%28%281%2F2%29%2Ax%2B%281%2F3%29%2Ay%29=%286%29%2A%2811%29\" Multiply both sides by the LCD 6
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\n" ); document.write( " \"3%2Ax%2B2%2Ay=66\" Distribute and simplify
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\n" ); document.write( " Lets start with the given system of linear equations
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\n" ); document.write( " \"1%2Ax%2B1%2Ay=27\"
\n" ); document.write( " \"3%2Ax%2B2%2Ay=66\"
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\n" ); document.write( " Now in order to solve this system by using substitution, we need to solve (or isolate) one variable. I'm going to choose y.
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\n" ); document.write( " Solve for y for the first equation
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\n" ); document.write( " \"1%2Ay=27-1%2Ax\"Subtract \"1%2Ax\" from both sides
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\n" ); document.write( " \"y=%2827-1%2Ax%29\" Divide both sides by 1.
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\n" ); document.write( " Which breaks down and reduces to
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\n" ); document.write( " \"y=27-1%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"27-1%2Ax\" we can substitute the expression \"27-1%2Ax\" into y of the 2nd equation. This will eliminate y so we can solve for x.
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\n" ); document.write( " \"3%2Ax%2B2%2Ahighlight%28%2827-1%2Ax%29%29=66\" Replace y with \"27-1%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"3%2Ax%2B2%2A%2827%29%2B2%28-1%29x=66\" Distribute 2 to \"27-1%2Ax\"
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\n" ); document.write( " \"3%2Ax%2B54-2%2Ax=66\" Multiply
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\n" ); document.write( " \"3%2Ax%2B54-2%2Ax=66\" Reduce any fractions
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\n" ); document.write( " \"3%2Ax-2%2Ax=66-54\" Subtract \"54\" from both sides
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\n" ); document.write( " \"3%2Ax-2%2Ax=12\" Combine the terms on the right side
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\n" ); document.write( " \"1%2Ax=12\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F1%29%281%2F1%29%29x=%2812%2F1%29%281%2F1%29\" Multiply both sides by \"1%2F1\". This will cancel out \"1%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"12%2F1\" and \"1%2F1\" (and simplify) we get
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\n" ); document.write( " \"x=12\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=12\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"3%2812%29%2B2%2Ay=66\" Plug in \"x=12\" into the 2nd equation
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\n" ); document.write( " \"36%2B2%2Ay=66\" Multiply
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\n" ); document.write( " \"2%2Ay=66-36\"Subtract \"36\" from both sides
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\n" ); document.write( " \"2%2Ay=30\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F2%29%282%29%29%2Ay=%2830%2F1%29%281%2F2%29\" Multiply both sides by \"1%2F2\". This will cancel out 2 on the left side.
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\n" ); document.write( " \"y=30%2F2\" Multiply the terms on the right side
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\n" ); document.write( " \"y=15\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=15\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=12\" and \"y=15\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"12\",\"15\")
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\n" ); document.write( " Notice if we graph the equations (if you need help with graphing, check out this solver)
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\n" ); document.write( " \"1%2Ax%2B1%2Ay=27\"
\n" ); document.write( " \"3%2Ax%2B2%2Ay=66\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax%2B1%2Ay=27\" (red) and \"3%2Ax%2B2%2Ay=66\" (green) (hint: you may have to solve for y to graph these) intersecting at the blue circle.
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\n" ); document.write( " and we can see that the two equations intersect at (\"12\",\"15\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"12\",\"15\") into the system of equations
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\n" ); document.write( " Let \"x=12\" and \"y=15\". Now plug those values into the equation \"1%2Ax%2B1%2Ay=27\"
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\n" ); document.write( " \"1%2A%2812%29%2B1%2A%2815%29=27\" Plug in \"x=12\" and \"y=15\"
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\n" ); document.write( " \"12%2B15=27\" Multiply
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\n" ); document.write( " \"27=27\" Add
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\n" ); document.write( " \"27=27\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"12\",\"15\") satisfies \"1%2Ax%2B1%2Ay=27\"
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\n" ); document.write( " Let \"x=12\" and \"y=15\". Now plug those values into the equation \"3%2Ax%2B2%2Ay=66\"
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\n" ); document.write( " \"3%2A%2812%29%2B2%2A%2815%29=66\" Plug in \"x=12\" and \"y=15\"
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\n" ); document.write( " \"36%2B30=66\" Multiply
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\n" ); document.write( " \"66=66\" Add
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\n" ); document.write( " \"66=66\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"12\",\"15\") satisfies \"3%2Ax%2B2%2Ay=66\"
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\n" ); document.write( " Since the solution (\"12\",\"15\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax%2B1%2Ay=27\"
\n" ); document.write( " \"3%2Ax%2B2%2Ay=66\"
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\n" ); document.write( " this verifies our answer.
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\n" ); document.write( "\n" ); document.write( "So our two numbers are: 12 and 15\r
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\n" ); document.write( "\n" ); document.write( "Notice 12+15=27 and \"%281%2F2%2912%2B%281%2F3%2915=6%2B5=11\". So this verifies our answer.
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