Question

Terry can run 15 miles in the same amount of time it takes Mark to run 21 miles. If Mark runs 2 mph faster than Terry, How fast does Mark run?

Answer 1

The amount of time required to travel a certain distance is equal to quotient of distance and speed. We let x be the speed of Terry and Mark's will be x+2. The equation that would best represent the scenario is,
15/x = 21/(x+2)
The value of x is 5. Thus, Mark's speed is 7 mph.