Britt finds that when she drives her boat upstream she can travel with a speed of 8m/s, but she can move with a speed of 12m/s when heads downstream. What is the current of the river that Britt is driving on?
12 - 8 = 4 m/s - difference in boat's speed due to the current
4 / 2 = 2 m/s - the speed of the current.