Question

David bought 3 dvds for for books for $40 at a yard sale in about one dvd and six books for $18 how much did each dvd cost

Answer 1

The system:
3 x + 4 y = 40
x + 6 y = 18,
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x = 18 - 6 y
3 ( 18 - 6 y ) + 4 y = 40
54 - 18 y + 4 y = 40
54 - 40 = 18 y - 4 y
14 = 14 y
y = $1
x = 18 - 6
x = $12
Answer: Each DVD costs: $12.