6 part a b and c show all work how do we do that ?

6) An object moves with constant acceleration. At t = 2.50 s, the position of the object is x = 2.00 m and its velocity is v = 4.50 m/s. At t= 7.00 s, v= -12.0 m/s. Find: (a) the position and the velocity at t = 0; (b) the average speed from 2.50 s to 7.00 s, and (c) the average velocity from 2.50 s to 7.00 s