how many pieces of wood measuring 12-inch by 13-inch can be cut from 48-inch by 72-inch piece of wood

Area problem

12 in x 13 in = 156 in²
48 in x 72 in = 3456 in²

3456 / 156 ≈ 22

You can cut 22 pieces of 12x13's from a 48x72.