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

Each DVD costs 12 dollars and each book costs 1 dollar

Explanation:

I think you meant: David bought 3 DVDs and 4 books for $40 at a yard sale. Anna bought one DVD and 6 books for $18. How much did each dvd and book cost?

Answer 2

The system:
3 x + 4 y = 40
x + 6 y = 18,
-------------------
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.