Question: Christian is twice as old as Brian. In eight more years, Brian will be 40 years old. How old will Christian be in eight years?
Answer with step-by-step thinking: If in eight years Brian will be 40 years old, he is currently 40 - 8 = 32 years old. Since Christian is twice as old as Brian, he is 2 * 32 = 64 years old. In 8 years, Christian will be 64 + 8 = 72 years old.
So the answer is 72.

Question: Anthony keeps a bottle of vinegar in his cupboard for 2 years. Each year 20% of the vinegar evaporates. What percent of the vinegar is left after 2 years?
Answer with step-by-step thinking: First find what percent of the vinegar is still in the bottle after each year: 100% - 20% = 80%. Then multiply the amount of vinegar left after one year by the percentage left after each year to find how much is left after 2 years: 80% * 80% = 64%.
So the answer is 64.

Question: Claudia has 122 ounces of water and is filling up cups. She has 8-ounce glasses, 5-ounce glasses, and 4-ounce glasses. If she fills six 5 ounce glasses and four 8 ounce glasses, how many 4 ounce glasses can she fill with the remaining water?
Answer with step-by-step thinking:
She has used 32 ounces on 8 - ounce glasses because 4 x 8 = 32. She has used 30 ounces on the 5 - ounce glasses because 6 x 5 = 30. She has used 62 ounces in total because 32 + 30 = 62. She has 60 ounces left because 122 - 62 = 60. She can fill fifteen four - ounce glasses because 60 / 4 = 15.
So the answer is 15.