Answer: 
-2m/s²
Step-by-step explanation:
Given parameters: 
Initial velocity of the car = 25m/s 
Time taken = 10s 
Final velocity = 5m/s 
Unknown: 
Acceleration of the car = ? 
Solution: 
Acceleration is the rate of change of velocity with time. 
 It is mathematically expressed as: 
 Acceleration = 
 
 
 Acceleration = 
 =  -2m/s²
 =  -2m/s²