Our city has 2400 subscribers for HipHop magazines Of these, 1200 subscribe to Magazine A, 500 subscribe to Magazine B, and 100 subscribe to both. What is the probability that a subscriber selected at random subscribes to either Magazine A or B?

If I add the subscribers of magazine A and B together (which is 1700), and divide it by the total amount of subscribers then I get a very small fraction, which isn't right. I think.