The figure gives the acceleration a versus time t for a particle moving along an x axis. The a-axis scale is set by as = 15.0 m/s2. At t = -2.0 s, the particle's velocity is 9.00 m/s. What is its velocity at t = 6.0 s?

Answer 1

since a is apparently not constant, and all you provide is a single data point, it's hard to determine the velocity at any other time.