3 1/4 hours = 3 + 1/4 = 3 + 0.25 = 3.25. 2 1/2 hours = 2 + 1/2 = 2.5. To find out how much travel time can be saved by taking the express, simply subtract its travel time (which is shorter) from the regular's one. So 3.25 - 2.5 = 0.75 or 3/4. So the answer is B.
