Answer:
 v = 158 m / s
Explanation:
In this kinematic problem they give us the acceleration of the body, the position and speed of the initial moment, let's use the definition of acceleration
    a = dv / dt
    dv = a dt
We integrate
    ∫ d v = ∫ (2t + 1) dt
    v = 2 (2t²) + 1t
We evaluate between the initial time t = 0 that has speed (vo) 8 m/s and the final time t with speed v
    v -8 = 4t2 + t
We already have the velocity formula as a function of time, let's calculate for t = 6 s
     v = 8 + 4 6² +6
    Â
     v = 158 m / s