Answer:
3 books per box, 3 left over.
Step-by-step explanation:
Brian has 18 books, and he is packing them into 5 boxes. 18 is only divisible by 1, 3, 9, and 18.
1 x 5 = 5 books = 13 left over. Still enough to pack more books.
3 x 5 = 15 books = 3 left over. This is the answer, but let's check the others as well.
9 x 5 = 45 books. He doesn't have that many! He can't put 9 books in each box because it would only take 2 boxes he's using all 5.
18 x 5 = 90 books. We can clearly see this isn't the answer. He would only be able to put all 18 books in 1 box but he wants to use all 5 boxes.
There are 3 books in each box with 3 left over.
