Determine the acceleration (in m/s) of an object which

A. changes its velocity from 12.1 m/s to 23.5 m/s in 7.81 seconds

B. accelerates from 33.4 m/s to 18.9 m/s over a distance of 109 m

C. accelerates from 21.5 m/s to 8.9 m/s over a distance of 109 m

Please help!