Posted by **Tory Smith** on Saturday, January 15, 2011 at 5:33pm.

The cost of thirteen CDs and seven DVDs is $99.80; and the cost of seven DVDs and twelve CDs is $84.11.

- math -
**helper**, Saturday, January 15, 2011 at 5:52pm
want do you need to find?

this problem is not complete

- math -
**Jen**, Saturday, January 15, 2011 at 5:55pm
13c+7d=99.8

12c+7d=84.11

Multiply the 2nd equation by -1

13c+7d=99.8

-12c-7d=-84.11

c=

Plug that back into either original equation to solve for d.

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