3 There are 42 comic books, 63 math books, and 28 nature books. All books are
going to be divided into some stacks. The number of comic books in each
stack is the same, so do math books and nature books. The greatest possible
number of stacks is

To find the greatest possible number of stacks, we need to determine the greatest common divisor (GCD) of the numbers of each type of book: 42, 63, and 28. The prime factorization gives us 42 (2 x 3 x 7), 63 (3 x 3 x 7), and 28 (2 x 2 x 7). The GCD is found by taking the product of the lowest powers of common prime factors, which in this case is 7. Thus, the greatest possible number of stacks is 7.

Now, by dividing the total number of books by this GCD, we can find how many stacks we can create. For comic books: 42 ÷ 7 = 6 stacks; for math books: 63 ÷ 7 = 9 stacks; and for nature books: 28 ÷ 7 = 4 stacks. So, you can create 7 stacks, with each stack containing the same number of each type of book!