Answer: Pablo rides his bicycle at 18 mph
Step-by-step explanation:
Let x represent the speed at which Pablo rides his bicycle.
Miguel can drive four times as fast as Pablo can ride his bicycle. This means that the speed at which Miguel drives his car is 4x
Time = distance/speed
The time it takes Pablo to cover 72 miles is
72/x
The time it takes Miguel to cover 72 miles is
72/4x = 18/x
if it takes Pablo three hours longer than Miguel to travel 72 miles, it means that
72/x - 18/x = 3
Multiplying through by x, it becomes
72 - 18 = 3x
3x = 54
x = 54/3
x = 18 mph
