Math Question! please help! Explain how you find the answer!?

A man is walking on a railroad bridge that goes from A to B. When he is 3/8 of the way across the bridge he hears a train approaching, and it is known that the speed of the train is 60 mph. The man's rate of speed is such that if he runs toward A he will meet the train at A, and if he runs toward B the train will overtake him at that point. How fast can he run?