3 second head start = 3x 5 = 15 meters
difference in speed 8- 5 = 3 m/s 15 / 3 = 5 seconds when P catches Q (this 8 seconds after Q starts)
in 5 seconds P runs 5 * 8 = 40 meters this is when they are at the same point
60 meters left in the race will take P 60 m / 8 m/s = 7.5 seconds to finish