A stackable CD rack holds 20 CDs and costs $3. Mark has a collection of 120 CDs. How much will it cost him to buy enough racks to hold all of his CDs?

You would need $18 total to buy the racks needed.

Step-by-step explanation:

First, every 20 CDs needs a new rack, so you would divide 120 by 20.

120 / 20 = 6 racks

Second, you would multiply the price ($3) of a rack by how many racks needed.

3 * 6 = $18