Mark has 30 cd's. 40% are country music. 30% pop music. how many cds are other types of music?

So first you add 40 percent and 30 percent to get 70 percent. After you do that subtract it from 100 to get 30. 30% times 30 is 9 so the answer is 9 cds.

9 cd's because you multiply .7*30 and that is 21 so 30-21=9
 

The correct one is c.