Answer: 6m/s^2
Step-by-step explanation:
Given the information, it is possible to find the average acceleration of the car using the fact that average acceleration equal to the change in velocity over the change in time.
In this case the change in velocity (final velocity - initial velocity) is 120m/s - 65m/s = 55m/s. The change in time is given (9s), so to find the average acceleration you have to divide 55 by 9.
55/9 = 6.11m/s^2 (using the correct number significant figures would simply give you 6)