algebra

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Select the set of equations that represents the following situation: The cost of eleven CDs and twelve DVDs is $150.62; and the cost of one DVDs and twelve CDs is $116.07. How much do a CD and a DVD cost?
(Points : 3)
11x + 12y = 150.62; 12x + 1y = 116.07
11x • 12y = 150.62; 12x • 1y = 116.07
11x + 12y = 150.62; 1x + 12y = 116.07
11x • 12y = 150.62; 1x • 12y = 116.07

  • algebra -

    Eq1: 11X + 12Y = 150.62
    Eq2: 12X + Y = 116.07
    MultiplyEq2 by -12:
    11X + 12Y = 150.62
    -144X -12Y = -1392.84
    Sum: -133X = -1242.22
    X = -1242.22 / -133 = $9.34 = Cost of
    1 CD.

    Substitute 9.34 for X in Eq2:
    12*9.34 + Y = 116.07,
    112.08 + Y = 116.07,
    Y = 116.07 - 112.08 = $3.99 = Cost of 1 DVD.

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