Full question:

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 2.50s to 7.00 s, and

(c) the average velocity from 2.50s to 7.00 s.

I tried using the kinematic equations of motion for constant acceleration but my answers make no sense.