What you have to do is find a way to make sure each book is the same price and it lowers to 16. First rule out 1-10. It wouldn't be possible. Next, try and start with the even numbers (16, 18, 20, and so on). It can't be twenty because 20 x 8 equals 160 and you're left with 16 dollars, not 8. so it's either 14, 15, 16, 17, 18, or 19. I calculated with my calcuator that it's not any of the answers but 19. So try it out!
