Jennifer has a total of 212 + 310 + 502 = 1,024 sweets. Jennifer and her friends will get 1,024 / 4 = 256 sweets each.
The answer: 256
Reverse engineering the question: Jennifer decides to share her sweets between herself and her 3 friends. She has 212 green sweets, 310 blue sweets and 502 yellow sweets. How many sweets will Jennifer and her friends get each?

Tyler gives away 21 / 3 = 7 CDs. After giving away a third of his CDs, Tyler has 21 - 7 = 14 CDs. After buying new CDs, Tyler has 14 + 8 = 22 CDs.
The answer: 22
Reverse engineering the question: Tyler has 21 CDs. He gives away a third of his CDs to his friend. Then he goes to the music store and buys 8 brand new CDs. How many CDs does Tyler have now?

Janine has 2 * 3 = 6 bottle caps. Sammy has 6 + 2 = 8 bottle caps.
The answer: 8
Reverse engineering the question: Sammy has 2 more bottle caps than Janine. Janine has 3 times as many bottle caps as Billie. If Billie has 2 bottle caps, how many does Sammy have?

The normal price of the lessons would be 20 * 40 = $800. The discount saves him 800 * .25 = $200. So the lessons cost him 800 - 200 = $600. That means everything costs 500 + 600 = $1100.
The answer: 1100
Reverse engineering the question:
John decides to learn how to play the piano. He buys a piano for $500. He then hires a teacher for 20 lessons at $40 per lesson but ends up getting a 25% discount. How much did everything cost?