document.write( "Question 1063749: Three pens and three notebooks cost $6.90. Two notebooks and one pen cost $4.10. Model this by useing a system of linear equations \n" ); document.write( "

Algebra.Com's Answer #678875 by ikleyn(52781) $\"\"$ $\"About$

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\n" ); document.write( "Three pens and three notebooks cost $6.90. Two notebooks and one pen cost $4.10. Model this by useing a system of linear equations
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document.write( "3p + 3n = 690,   (1)\r\n" );
document.write( "1p + 2n = 410    (2)\r\n" );
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document.write( "You asked to model it. I modelled it for you.\r\n" );
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document.write( "But let me add couple of words to it.\r\n" );
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document.write( "If \"Three pens and three notebooks cost $6.90\", then \r\n" );
document.write( "    one pen    and one   notebook cost one third of it, i.e. 690/3 = 230 cents, right ?\r\n" );
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document.write( "Next, if one pen and one notebook  cost 230 cents    and\r\n" );
document.write( "         one pen and two notebooks cost 410 cents,   THEN WHAT ?\r\n" );
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document.write( "But of course, then one notebook costs 410 - 230 = 180 cents = $1.80.\r\n" );
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document.write( "So, one half of the problem is just solved.\r\n" );
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document.write( "It is how the Elimination Method works.\r\n" );
document.write( "I explained it to you by using words, without equations.\r\n" );
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