Problem
6. David bought 3 DVDs for 4 books for $\$ 40$ at a yard sale. Anna bought 1 DVD and 6 books for $\$ 18$. How much did each DVD and book cost?
Solution
Step 1 ：Let's denote the cost of a DVD as D and the cost of a book as B.
Step 2 ：From the problem, we can derive two equations: \(3D + 4B = 40\) and \(D + 6B = 18\).
Step 3 ：We can solve this system of equations to find the values of D and B.
Step 4 ：The solution to the system of equations is {B: 1, D: 12}.
Step 5 ：The cost of each DVD is \(\boxed{12}\) dollars and the cost of each book is \(\boxed{1}\) dollar.
