document.write( "Question 189716: The sum of two numbers is 99. If 10 times the smaller is decreased by 2 times the larger, the result is 30. Find the numbers. \n" ); document.write( "
Algebra.Com's Answer #142361 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Let \r
\n" ); document.write( "\n" ); document.write( "x = smaller number\r
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\n" ); document.write( "\n" ); document.write( "\"The sum of two numbers is 99\" translates to \"x%2By=99\" and\r
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\n" ); document.write( "\n" ); document.write( "\"If 10 times the smaller is decreased by 2 times the larger, the result is 30\" translates to \"10x-2y=30\"\r
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\n" ); document.write( "\n" ); document.write( "Start with the given system of equations:\r
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\n" ); document.write( "\n" ); document.write( "\"system%28x%2By=99%2C10x-2y=30%29\"\r
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\n" ); document.write( "\n" ); document.write( "Let's solve by substitution\r
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\n" ); document.write( "\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 solve for y.\r
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\n" ); document.write( "\n" ); document.write( "So let's isolate y in the first equation\r
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\n" ); document.write( "\n" ); document.write( "\"x%2By=99\" Start with the first equation\r
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\n" ); document.write( "\n" ); document.write( "\"y=99-x\" Subtract \"x\" from both sides\r
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\n" ); document.write( "\n" ); document.write( "\"y=-x%2B99\" Rearrange the equation\r
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\n" ); document.write( "\n" ); document.write( "Since \"y=-x%2B99\", we can now replace each \"y\" in the second equation with \"-x%2B99\" to solve for \"x\"\r
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\n" ); document.write( "\n" ); document.write( "\"10x-2highlight%28%28-x%2B99%29%29=30\" Plug in \"y=-x%2B99\" into the second equation. In other words, replace each \"y\" with \"-x%2B99\". Notice we've eliminated the \"y\" variables. So we now have a simple equation with one unknown.\r
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\n" ); document.write( "\n" ); document.write( "\"10x%2B%28-2%29%28-1%29x%2B%28-2%29%2899%29=30\" Distribute \"-2\" to \"-x%2B99\"\r
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\n" ); document.write( "\n" ); document.write( "\"10x%2B2x-198=30\" Multiply\r
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\n" ); document.write( "\n" ); document.write( "\"12x-198=30\" Combine like terms on the left side\r
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\n" ); document.write( "\n" ); document.write( "\"12x=30%2B198\"Add 198 to both sides\r
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\n" ); document.write( "\n" ); document.write( "\"12x=228\" Combine like terms on the right side\r
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\n" ); document.write( "\n" ); document.write( "\"x=%28228%29%2F%2812%29\" Divide both sides by 12 to isolate x\r
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\n" ); document.write( "\n" ); document.write( "\"x=19\" Divide\r
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\n" ); document.write( "\n" ); document.write( "-----------------First Answer------------------------------\r
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\n" ); document.write( "\n" ); document.write( "So the first part of our answer is: \"x=19\"\r
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\n" ); document.write( "\n" ); document.write( "Since we know that \"x=19\" we can plug it into the equation \"y=-x%2B99\" (remember we previously solved for \"y\" in the first equation).\r
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\n" ); document.write( "\n" ); document.write( "\"y=-x%2B99\" Start with the equation where \"y\" was previously isolated.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-%2819%29%2B99\" Plug in \"x=19\"\r
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\n" ); document.write( "\n" ); document.write( "\"y=-19%2B99\" Multiply\r
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\n" ); document.write( "\n" ); document.write( "\"y=80\" Combine like terms \r
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\n" ); document.write( "\n" ); document.write( "-----------------Second Answer------------------------------\r
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\n" ); document.write( "\n" ); document.write( "So the second part of our answer is: \"y=80\"\r
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\n" ); document.write( "\n" ); document.write( "-----------------Summary------------------------------\r
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\n" ); document.write( "\n" ); document.write( "So our answers are:\r
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\n" ); document.write( "\n" ); document.write( "\"x=19\" and \"y=80\"\r
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\n" ); document.write( "\n" ); document.write( "This means that the smaller number is 19 and the larger number is 80
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