Answer:
15 CDs
Explanation:
The total percentage of the CDs is 100% because it basically means all the CDs. Therefore, the percentages of types need to add up to 100%. If 30% are country and 40% are pop, 100 - 30 - 40 = 30% are other.
30% is equivalent to 30/100 or 0.3 when written as a decimal. You would then multiply this by the number of CDs to get the number of other CDs:

Therefore, 15 CDs are other types of music