Question

Perry was going to sell all of his stamp collection to buy a video game. After selling half of them he changed his mind. He then bought fifteen more. How many did he start with if he now has 34?

Answer 1

The answer is 38, because if you take away the 15 he bought afterwards (34-15) you get 19, and then since he sold half his collection you would double that (19×2) and that's 38.