A :-) for this question , we should apply 
a = v - u by t 
Given - u = -2 m/s 
              v = -10 m/s 
              t = 16 sec 
Solution - 
a = v - u by t 
a = -10 - -2 by 16 
a = -12 by 16 
( cut 12 and 16 because 2 x 6 = 12 and 
2 x 8 = 16 ) 
( cut 6 and 8 because 2 x 3 = 6 and 
2 x 4 = 8 ) 
a = 3 by 4 
a = 0.75 m/s^2 
.:. The acceleration is 0.75 m/s^2.