document.write( "Question 769353: Kenny paid $120 for 4 cds and 3 dvds. Each dvd cost $12 more than a cd. what was the cost of three dvds? \n" ); document.write( "

Algebra.Com's Answer #468812 by Jc0110(165) $\"\"$ $\"About$

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Let the cost of 1 CD to be x whereas the cost of 1 DVD to be y.
\n" ); document.write( " $\"4x%2B3y=120\"$ ---> Equation 1
\n" ); document.write( " $\"y=x%2B12\"$ ---> Equation 2 ... Substitute $\"y=x%2B12\"$ into Equation 1
\n" ); document.write( " $\"4x%2B3%28x%2B12%29=120\"$
\n" ); document.write( " $\"4x%2B3x%2B36=120\"$
\n" ); document.write( " $\"4x%2B3x=120-36\"$
\n" ); document.write( " $\"7x=84\"$
\n" ); document.write( " $\"x=84%2F7\"$
\n" ); document.write( " $\"x=12\"$ ... Substitute $\"x=12\"$ into Equation 1
\n" ); document.write( " $\"4%2812%29%2B3y=120\"$
\n" ); document.write( " $\"48%2B3y=120\"$
\n" ); document.write( " $\"highlight%283y%29=120-48\"$ ---> 3y is made as the subject of the equation because the cost of 1 DVD is y, thus the cost of 3 DVDs is 3y.
\n" ); document.write( " $\"3y=72\"$
\n" ); document.write( "Thus, the cost of 3 DVDs is $72. \n" ); document.write( "

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