Work is done when a force acts over a distance. Remember the formula: work done = force × distance.
If we know the braking distance of the car, we can clearly do some calculations here!
To bring a car to a stop, its kinetic energy must be lost to other forms, such as heat or sound. To do this, work must be done by its brakes. It should be obvious then that:
Work Done Braking = Initial Kinetic Energy of Car