Step-by-step explanation: They need to cover expense of $13200. If printing fee is $25 and they sell the books for $40 each, then that means when selling a book they cover expense of printing plus they earn $15 per book.
So if they earn $15 per book that means they have to sell 13200/15=880 books to break even.
If you want to solve this by using equation the this would look like this:
expenses: $13200 + $25x where x is number of books sold