Jenny is older than Charlie by five years, while Charlie is older than Bobby by three years. How old will Charlie be when Jenny becomes twice as old as Bobby? Give the rationale and then the answer.
Let's think step by step. Jenny is older than Charlie by 5 years who is older than Bobby by 3 years, so Jenny is older than Bobby by 5 + 3 = 8 years. Jenny will be twice as old as Bobby when he is 8 * 2 = 16 years old. Jenny is 5 years older than Charlie so when Jenny is 16, Charlie will be 16 - 5 = 11 years old.. The answer is: 11.

Jill bought 5 packs of red bouncy balls and 4 packs of yellow bouncy balls. Each package contained 18 bouncy balls. How many more red bouncy balls than yellow bouncy balls did Jill buy? Give the rationale and then the answer.
Let's think step by step. Jill bought 5 packs * 18 red balls = 90 red balls. Jill bought 4 packs * 18 yellow balls = 72 red balls. Jill had 90 red – 72 yellow = 18 more red balls.. The answer is: 18.

My brother and I have thirty minutes to go to school, without being late. It takes us 15 minutes to arrive at the school gate, and another 6 minutes to get to the school building. How much time do we have to get to our room, without being late? Give the rationale and then the answer.
Let's think step by step. The total time we spent going to school is 15 minutes + 6 minutes = 21 minutes. We have 30 minutes - 21 minutes = 9 minutes left not to be late.. The answer is: 9.