Answer:
The deceleration of the car is

Step-by-step explanation:
It is given that,
Mass of the car, m = 1200 kg
Initial speed of the car, u = 20 m/s
Friction brings the car to rest, final speed, v = 0
The coefficient of friction between the tires and road is 0.8
Let a is the deceleration of car due to force of friction. The frictional force is given by :






So, the deceleration of the car is
. Hence, this is the required solution.