document.write( "Question 362437: Bob bought 1 pen and 4 pencils for $1.65. Joe bought 4 pens and 1 pencli for $3.75. How much is a pen \n" ); document.write( "

Algebra.Com's Answer #258327 by HasanSahin(52) $\"\"$ $\"About$

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Let's say pen = A, and pencil = B,\r
\n" ); document.write( "\n" ); document.write( "Bob >> A + 4B = $1.65\r
\n" ); document.write( "\n" ); document.write( "Joe >> 4A + B = $3.75\r
\n" ); document.write( "\n" ); document.write( "You have 2 unknowns and 2 equations. But you must need one unknown and one equation in order to solve this problem.Therefore you must wipe out one variable.For example I want to wipe out A therefore I Multiply the first(Bob's) equation by 4.\r
\n" ); document.write( "\n" ); document.write( "It looks like now:
\n" ); document.write( "Bob >> 4A + 16B = $6.6\r
\n" ); document.write( "\n" ); document.write( "Joe >> 4A + B = $3.75\r
\n" ); document.write( "\n" ); document.write( "You have to subtract Joe's equation from Bob's equation in order to wipe out A.\r
\n" ); document.write( "\n" ); document.write( "4A + 16B = $6.6\r
\n" ); document.write( "\n" ); document.write( "4A + B = $3.75
\n" ); document.write( "__________________\r
\n" ); document.write( "\n" ); document.write( "0A + 15B = $2.85 Therefore you get 15B = $2.85 and you can find B as $0.19\r
\n" ); document.write( "\n" ); document.write( "and if you put B into any equation such as 4A + B = $3.75\r
\n" ); document.write( "\n" ); document.write( "you get 4A + $0.19 = $3.75 and when you solve this you get A as $0.89\r
\n" ); document.write( "\n" ); document.write( "RF. \n" ); document.write( "

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