Answer:

Negative sign shows that velocity of the car is decreases at a constant rate
Explanation:
We have given velocity of the car is decreases from 32 m /sec to 24 m/sec in 4 second
So initial velocity of the car u = 32 m /sec
And finally car reaches to a velocity of 24 m/sec
Time taken to change in velocity = 4 sec
So final velocity v = 24 m/sec
From first equation of motion v = u+at
So 

Negative sign shows that velocity of the car is decreases at a constant rate
Answer:
your language is to different to mine sorry
The acceleration of the car is solved by subtracting the initial speed from the final speed then dividing the result by the elapsed time.
initial speed = 72 km/hr = 20 m/s
final speed = 0 m/s
elapsed time = 5 seconds
acceleration = (0 m/s – 20 m/s) / 5 s
acceleration = - 20m/s / 5 s
acceleration = -4 m/s^2
Answer a would be correct since velocity is a vector and has a magnitude and a direction. In this case v₁ = - v₂.