Question 203553
This one is solved by using the formula  time = distance / velocity.

Let the velocity of the express train be v miles per hour.

The time taken for the express train to complete the journey (call it t1) 

t1 = 60/v

Now, we know that the speed of the local train is HALF that of the express train (ie equals 0.5v), so we can use the same formula to calculate the time (call it t2) it takes the local train to complete the journey

t2 = 60 / (0.5v) = 120/v

The difference in times is two hours

t2 - t1 = 2    (its t2 minus t1 because t2 is the longer time)

(120 - 60)/v = 2  (substituting)

60/v = 2

v = 30 mph

So the express train goes at 30mph and therefore travels the 60 miles in 2 hours

The local train goes at 15mph and therefore takes 4 hours, ie two hours longer.