document.write( "Question 97035: Adult tickets for a play cost $9 and child tickets cost $8. If there were 23 people at a performance and the theater collected $193 from ticket sales, how many children attended the play? \n" ); document.write( "
Algebra.Com's Answer #70629 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Let x=# of children, y=# of adults\r
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\n" ); document.write( "\n" ); document.write( "Set up the following system\r
\n" ); document.write( "\n" ); document.write( "\"x%2By=23\" \"If there were 23 people at a performance\"
\n" ); document.write( "\"8x%2B9y=193\" \"Adult tickets for a play cost $9 and child tickets cost $8\"\r
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Solved by pluggable solver: Solving a linear system of equations by subsitution

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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=23\"
\n" ); document.write( " \"8%2Ax%2B9%2Ay=193\"
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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=23-1%2Ax\"Subtract \"1%2Ax\" from both sides
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\n" ); document.write( " \"y=%2823-1%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=23-1%2Ax\" Now we've fully isolated y
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\n" ); document.write( " Since y equals \"23-1%2Ax\" we can substitute the expression \"23-1%2Ax\" into y of the 2nd equation. This will eliminate y so we can solve for x.
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\n" ); document.write( " \"8%2Ax%2B9%2Ahighlight%28%2823-1%2Ax%29%29=193\" Replace y with \"23-1%2Ax\". Since this eliminates y, we can now solve for x.
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\n" ); document.write( " \"8%2Ax%2B9%2A%2823%29%2B9%28-1%29x=193\" Distribute 9 to \"23-1%2Ax\"
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\n" ); document.write( " \"8%2Ax%2B207-9%2Ax=193\" Multiply
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\n" ); document.write( " \"8%2Ax%2B207-9%2Ax=193\" Reduce any fractions
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\n" ); document.write( " \"8%2Ax-9%2Ax=193-207\" Subtract \"207\" from both sides
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\n" ); document.write( " \"8%2Ax-9%2Ax=-14\" Combine the terms on the right side
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\n" ); document.write( " \"-1%2Ax=-14\" Now combine the terms on the left side.
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\n" ); document.write( " \"cross%28%281%2F-1%29%28-1%2F1%29%29x=%28-14%2F1%29%281%2F-1%29\" Multiply both sides by \"1%2F-1\". This will cancel out \"-1%2F1\" and isolate x
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\n" ); document.write( " So when we multiply \"-14%2F1\" and \"1%2F-1\" (and simplify) we get
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\n" ); document.write( " \"x=14\" <---------------------------------One answer
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\n" ); document.write( " Now that we know that \"x=14\", lets substitute that in for x to solve for y
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\n" ); document.write( " \"8%2814%29%2B9%2Ay=193\" Plug in \"x=14\" into the 2nd equation
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\n" ); document.write( " \"112%2B9%2Ay=193\" Multiply
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\n" ); document.write( " \"9%2Ay=193-112\"Subtract \"112\" from both sides
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\n" ); document.write( " \"9%2Ay=81\" Combine the terms on the right side
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\n" ); document.write( " \"cross%28%281%2F9%29%289%29%29%2Ay=%2881%2F1%29%281%2F9%29\" Multiply both sides by \"1%2F9\". This will cancel out 9 on the left side.
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\n" ); document.write( " \"y=81%2F9\" Multiply the terms on the right side
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\n" ); document.write( " \"y=9\" Reduce
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\n" ); document.write( " So this is the other answer
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\n" ); document.write( " \"y=9\"<---------------------------------Other answer
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\n" ); document.write( " So our solution is
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\n" ); document.write( " \"x=14\" and \"y=9\"
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\n" ); document.write( " which can also look like
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\n" ); document.write( " (\"14\",\"9\")
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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=23\"
\n" ); document.write( " \"8%2Ax%2B9%2Ay=193\"
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\n" ); document.write( " we get
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\n" ); document.write( " graph of \"1%2Ax%2B1%2Ay=23\" (red) and \"8%2Ax%2B9%2Ay=193\" (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 (\"14\",\"9\"). This verifies our answer.
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\n" ); document.write( " Check:
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\n" ); document.write( " Plug in (\"14\",\"9\") into the system of equations
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\n" ); document.write( " Let \"x=14\" and \"y=9\". Now plug those values into the equation \"1%2Ax%2B1%2Ay=23\"
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\n" ); document.write( " \"1%2A%2814%29%2B1%2A%289%29=23\" Plug in \"x=14\" and \"y=9\"
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\n" ); document.write( " \"14%2B9=23\" Multiply
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\n" ); document.write( " \"23=23\" Add
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\n" ); document.write( " \"23=23\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"14\",\"9\") satisfies \"1%2Ax%2B1%2Ay=23\"
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\n" ); document.write( " Let \"x=14\" and \"y=9\". Now plug those values into the equation \"8%2Ax%2B9%2Ay=193\"
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\n" ); document.write( " \"8%2A%2814%29%2B9%2A%289%29=193\" Plug in \"x=14\" and \"y=9\"
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\n" ); document.write( " \"112%2B81=193\" Multiply
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\n" ); document.write( " \"193=193\" Add
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\n" ); document.write( " \"193=193\" Reduce. Since this equation is true the solution works.
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\n" ); document.write( " So the solution (\"14\",\"9\") satisfies \"8%2Ax%2B9%2Ay=193\"
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\n" ); document.write( " Since the solution (\"14\",\"9\") satisfies the system of equations
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\n" ); document.write( " \"1%2Ax%2B1%2Ay=23\"
\n" ); document.write( " \"8%2Ax%2B9%2Ay=193\"
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\n" ); document.write( " this verifies our answer.
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\n" ); document.write( "\n" ); document.write( "So that means 14 children and 9 adults attended the play
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