document.write( "Question 737557: \r
\n" ); document.write( "\n" ); document.write( "Three CD's cost and four DVD's cost $108. Five CD's and three DVD's cost $114. Find the cost of one CD and one DVD.
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Algebra.Com's Answer #450431 by checkley79(3341)\"\" \"About 
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3C+4D=108 MULTIPLY BY 3
\n" ); document.write( "5C+3D=114 MULTIPLY BY -4 & ADD
\n" ); document.write( "9C+12D=324
\n" ); document.write( "-20C-12D=-456
\n" ); document.write( "-------------------
\n" ); document.write( "-11C=-132
\n" ); document.write( "C=-132/-11
\n" ); document.write( "C=$12 COST OF 1 CD.
\n" ); document.write( "3*12+4D=108
\n" ); document.write( "36+4D=108
\n" ); document.write( "4D=108-36
\n" ); document.write( "4D=72
\n" ); document.write( "D=72/4
\n" ); document.write( "D=$18 COST OF 1 DVD.
\n" ); document.write( "PROOF:
\n" ); document.write( "5*12+3*18=114
\n" ); document.write( "60+54=114
\n" ); document.write( "114=114
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