Is there answer options because if not then it would possibly be y = 45x + 540 or it could be 45x = 540 or it could be 45x/540 so it can be any of those :)
So each book is an average of 2.8 cm so 120 divided by each book=number of books 120/2.8=42.85 round down since you can't fit .85 of a book on a shelf the answer is 42 books
