Question

Maurice drove 400 km from Edmonton to Battleford in 1 hour less time than it took Martin to drive the same route from Battleford to Edmonton. If Maurice drove 20 km/h faster than Martin, at what speed did each of them drive?
Show a complete algebraic solution.

Let V = Maurice's speed and v = Martin's speed, measured in km/h.

V = v + 20

Maurice's time = 400/V = Martin's time - 1 = 400/v - 1
400/V = 400/v - 1

You now have two equations in two unknowns, V and v. Sove them by standard algebraic methods. One way would be to substitute v+20 for V in the second equation, and solve for the remaining unknown v.