ANSWER = 22
First you can buy 15 chocolates. These gives you 15 wrappers.
The 15 wrappers can be exchanged to 5 chocolates. These give you 5 wrappers.
Of these 5 wrappers, 3 can be exchanged to yet one chocolate, giving you one wrapper.
You had 2 wrappers left from the 5. Together with the one...