Car B will intercept Car A in 4 hours after Car B left the town. There is a 5 mile/hour difference between Car A and Car B velocity and Car B has more velocity than Car A. This difference shows Car B's ability to intercept Car A in a specified amount of time. In first 1 hour, Car A already traveled for 20 miles and Car B need 4 hours (=20/5) to close that distance gap for intercepting Car A.
