Q: Amy's grandfather gave her $100 for her birthday. Amy bought 3 dolls, each of which cost $1. How much money does Amy have left?
A: The cost of the dolls is 3 × $1 = $3. Amy has $100 − $3 = $97 left. The answer is 97.

Q: Jerry mows 8 acres of lawn each week. He mows ¾ of it with a riding mower that can cut 2 acres an hour. He mows the rest with a push mower that can cut 1 acre an hour. How long does Jerry mow each week?
A: Jerry mows 8 acres x ¾ = 6 acres with a riding mower. It will take him 6 acres / 2 each hour = 3 hours. Jerry mows 8 acres – 6 acres mowed with a riding mower = 2 acres with a push mower. It will take him 2 acres x 1 hour = 2 hours. It takes Jerry a total of 3 hours on the riding mower + 2 hours on the push mower = 5 hours. The answer is 5.

Q: Annabelle collected a weekly allowance of $30. She spent a third of it buying junk food, then spent another $8 on sweets. Out of guilt she decides to save the rest. How much did she save?
A:
A third of $30 is $30 * (1 / 3) = $10. She spent $10 from $30 leaving $30 - $10 = $20. She spent another $8 leaving $20 - $8 = $12 which she saved. The answer is 12.