Annie starts with 21 + 36 = 57 crayons. Bobby ends up giving her 36 / 2 = 18 crayons. Annie now has a total of 57 + 18 = 75 crayons. She ends up giving Mary a total of 75 * (1 / 3) = 25 crayons.
The answer: 25
Reverse engineering the question: Annie was given a pack of crayons. The pack contained 21 crayons. She already had a box of 36 crayons in her locker. Her friend Bobby gave her half the amount she already had in her locker. She decided to give her sister Mary 1/3 of her total amount of crayons. How many crayons does she give to Mary?

Wearing the high - tech shoes, Candace can hike 6 mph * 2 = 12 mph for the first two hours. Then she gets one blister, so her speed drops to 12 mph - 2 mph = 10 mph for the next two hours of the hike. After that time Candace gets another blister, but 2 hours + 2 hours = 4 hours, so the hike is over and we don't care about her speed anymore. Candace spends an equal amount of time walking at 12 mph and 10 mph, so we can average the two speeds to find an overall speed of (12 mph + 10 mph) / 2 = 11 mph.
The answer: 11
Reverse engineering the question: Candace is trying to decide whether to wear her old shoes or new high-tech shoes for a hike. The high-tech shoes will help Candace walk twice as fast, but they're not broken in yet, so she'll get 1 blister after every 2 hours she spends walking in them. Each blister slows Candance down by 2 miles per hour. If Candance walks 6 miles per hour in the old shoes and plans to hike for 4 hours, how many miles per hour can she go in the new shoes?

The carpenters need to produce 75 / 50 = 1.5 times as many chairs in the same number of days. It will require 1.5 times as many carpenters to produce the extra chairs, so 8 * 1.5 = 12 carpenters will be required.
The answer: 12
Reverse engineering the question: If 8 carpenters can make 50 chairs in 10 days, how many carpenters are needed to make 75 chairs in 10 days?

They'll need to make an estimated 0.5 * 53 = 26.5 omelets for small children. They'll need to make an estimated 1 * 35 = 35 omelets for older children. They'll need to make an estimated 2 * 75 = 150 omelets for the adults. And they'll need to make an estimated 1.5 * 37 = 55.5 omelets for the seniors. Along with the 25 extra omelets they'll make as a buffer, they will need enough eggs for 26.5 + 35 + 150 + 55.5 + 25 = 292 omelets. So they will need 2 * 292 = 584 eggs.
The answer: 584
Reverse engineering the question:
The Rotary Club is holding its annual fundraising Omelet Breakfast, with tickets sold in advance. The tickets come in different price levels, for young children, older children, adults, and seniors. This year they sold 53 small children tickets, 35 older children tickets, 75 adult tickets, and 37 senior tickets. To figure out how many eggs they need to buy, the club estimates that small children can eat a half omelet, older children can eat a whole omelet, adults will eat two omelets, and seniors will eat one and a half omelets. Just to be on the safe side, they get enough eggs to make 25 extra omelets. If they use 2 eggs for each omelet, how many eggs will they need to buy?