Increasing the average speed of a car by 12mph results in a 189 mile trip taking an hour less than before. What was the original speed of the car?

To answer this item, we let the original speed of the car be x. The time it take to travel a certain distance is calculated by dividing the distance by the speed. Using the condition given above,

189 / (x + 12) = 189/x - 1

The value of x from the equation is 42 mph. Thus, the original speed of the car is 42 mph.