Crystal has 36 CDs. This is because she has 2 CDs in each 3 boxes on 6 shelves. 2 x 3 x 6 is a simple expression that can be used to find the total amount of CDs Crystal has.
You could also use a picture to describe the problem. 00 - [] [] [] represents how many CDs are on 1 shelf. 00 = 2 CDs and [] [] [] = 3 boxes. Now multiply 00 - [] [] [] x 6 shelves and you get 36 CDs in total.
