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? Let's think first. Chain of thought:
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.