Question 403402
With $15 you can buy 15 apples and obtain 15 wrappers. These 15 wrappers can be traded to get five more apples, each of which comes with a wrapper. Trade three of the five leftover wrappers to get one more apple. Here you have one wrapper, plus two more wrappers from the leftover two apples, so you can obtain one last apple. Therefore the total number of apples is 15 + 5 + 1 + 1 = 22.