Problem: A car is initially coasting at an unknown speed, when the driver hits the brake, causing the car to slow down at a uniform rate of 3.00 m/s2. The car travels for 45.0 m with the brakes on before slowing to a speed of 15.0 m/s.
Part A: What was the speed at which the car was initially coasting?
Express your knowledge to solve the above question.