We know that Jose has 23 comic books, and we know that Jose has 9 more comic books than Robin, therefore Robin has 14 comic books. (23-9) We also know that Robin has five more comic books than Lee, so Lee must have 9 comic books (14-5)
The answer is 5 books. 1 book per 20 books, since its 100 books you do 100/20. Getting 5 times 20 went into those books, and because per stack of 20 you got 1 you end up with 5 books. Hope this helps :P
