Jack bought 3 books a month at $20 each. He sells them back at the end of the year for $500. How much money did he lose?
Think hard. Detailed solution:
220
He bought 3 * 20 = $60 of books a month.

That means he bought 60 * 12 = $720 of books a year.

So he lost 720 - 500 = $220.

.

Therefore, the answer is 220