I'm stuck on this one question and I don't quite get it.

The probability that a teenager enjoys rock music in 0.7, and the probability that a teenager enjoys country music is 0.2. If only 1 in 10 teenagers enjoys rock as well as country, what is the probability that a teenager at random listens to either rock or country?I don't quite understand where to break it up, where to put what numbers and what formula to use.