The right answer is B, because if the first one starts at 2 o'clock, in 7 1/2 hrs he will make 6*7 1/2 iaw 45 miles.The second one will starts at 5 o'clock so he will make in 4 1/2 * 10 45 miles too.So the second one will catch the first one at 9 1/2 o'clock
distance=speed*time
so first have v1 and the second one v2, the distance is the same, we have to find out the time t
d=v1*t
d=v2*(t-3) so v1*t=v2*t-3*v2 so v2*t -v1*t=3*v2 so t(v2-v1)=3v2 so t=3v2/ v2-v1 so 30/4 so 7,5 iaw 7 hrs and 30 minutes
so the time is 7 1/2 - 3 = 4 1/2