Q: Bob orders a pizza with 8 slices. He eats half of it and each slice was 300 calories. How many calories did he eat?
A: He ate 8 / 2 = 4 slices. So he ate 4 * 300 = 1200 calories. The answer is 1200.

Q: Steve finds 100 gold bars while visiting Oregon. He wants to distribute his gold bars evenly to his 4 friends. If 20 gold bars were lost on the way back to San Diego, how many gold bars will each of his 4 friends get when he returns?
A: He only has 100 - 20 = 80 gold bars after losing 20 of them. He then gives each of his friends 80 ÷ 4 = 20 gold bars. The answer is 20.

Q: Mary wants to bake 10 apple pies for a charity event. Each pie needs 8 apples and she already harvested 50 apples from the trees in her garden. How many more apples does she need to buy to make all 10 pies?
A:
She needs 10 * 8 = 80 apples to make the pies. So she has to buy 80 - 50 = 30 more apples. The answer is 30.