Stapless seing cd at 1/3 off regular price of 10 for $18 how much would 30 discs cost

Well, the deal the store Staples has is, buy 10 cds and you get them for $18, otherwise is more expensive.

now, if you buy 30, well, 30 is just 10 + 10 + 10, so their price will then just be 18 + 18 + 18.