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

  • math -

    want do you need to find?

    this problem is not complete

  • math -

    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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