document.write( "Question 1139492: Mark won a lottery and received $74,000; he invested part of it in his retirement account and donated the rest to a charity. The amount of the donation was $500 less than a quarter of the amount of the investment. How much did Mark invest in his retirement account and how much did he donate to the charity?\r
\n" ); document.write( "\n" ); document.write( "(a) Define your variable(s).\r
\n" ); document.write( "\n" ); document.write( "(b) Construct a mathematical model (equation) in one unknown.\r
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Algebra.Com's Answer #759982 by Theo(13342)\"\" \"About 
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mark wins the lottery and receives 74,00.
\n" ); document.write( "he invest part of it and donates the rest to charity.
\n" ); document.write( "the amount he donates is 500 less than a quarter of the amount of the investment.
\n" ); document.write( "how much did he invest in his retirement account and how much did he donate to charity.\r
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\n" ); document.write( "\n" ); document.write( "let x equal the amount he donated to charity.
\n" ); document.write( "74,000 is the amount he received.
\n" ); document.write( "the amount he donated is 500 less than one quarter of the amount of the investment.\r
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\n" ); document.write( "\n" ); document.write( "if we let x equal the amount he donaterd to charity and if we let y equal the amount he invested, we get:\r
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\n" ); document.write( "\n" ); document.write( "x + y = 74,000
\n" ); document.write( "x = 1/4 * y - 500\r
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\n" ); document.write( "\n" ); document.write( "replace x with 1/4 * y - 500 in the equation of x + y = 74,000 to get:\r
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\n" ); document.write( "\n" ); document.write( "1/4 * y - 500 + y = 74,000\r
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\n" ); document.write( "\n" ); document.write( "add 500 to both sides of this equation to get 1/4 * y + y = 74,500.\r
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\n" ); document.write( "\n" ); document.write( "combine like terms to get 5/4 * y = 74,500\r
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\n" ); document.write( "\n" ); document.write( "solve for y to get y = 74,500 * 4/5 = 59,600.\r
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\n" ); document.write( "\n" ); document.write( "since x + y = 74,000, then x must be equal to 74,000 - 59,600 = 14,400.\r
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\n" ); document.write( "\n" ); document.write( "it appears that your solution is that he invested 59,600 in his retirement account and he donated 14,400 to charity.\r
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\n" ); document.write( "\n" ); document.write( "all we need to do is to confirm that this is correct.\r
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\n" ); document.write( "\n" ); document.write( "x + y = 74,000 becomes 14,400 + 59,600 = 74,000 which is true.\r
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\n" ); document.write( "\n" ); document.write( "x = 1/4 * y - 500 becomes x = 1/4 * 59,600 - 500 which becomes x = 14,400 which is true.\r
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\n" ); document.write( "\n" ); document.write( "the solution looks good.\r
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\n" ); document.write( "\n" ); document.write( "the solution is that he invested 59,600 in his retirement account and donates 14,400 to charity.\r
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