If you would like to know the speed of each runner, you can calculate this using the following steps:
6 miles ... x + 2.5 mile per hr (Suize)
4 miles ... x mile per hr (Jeff)
6 * x = 4 * (x + 2.5)
6 * x = 4 * x + 4 * 2.5
2 * x = 4 * 2.5
2 * x = 10
Jeff: x = 5 mile per hr
Suize: x + 2.5 = 5 + 2.5 = 7.5 mile per hr
Suize runs 7.5 mile per hr, and Jeff 5 mile per hr.
