David bought 3 DVDs and 4 book for $40 at a yard sale .anna bought 1 DVD and 6 books for $18 .How much did each DVD and a book cost

Answer 1

Let x = the cost of one DVD

Let y = the cost of one book

3x + 4y = 40

1x + 6y = 18 Multiply this equation by -3 and add to the first equation.

-3x - 18y = -54

3x + 4y = 40

-14y = -14

y = $1

x + 6(1) = 18

x = $12