A body starts at x = 0 with a velocity of 3 m/s, and its acceleration is a = 8 - 2t (SI units)…

Step 1. Velocity. $v = 3 + \int_0^t (8 - 2t)\,dt = 3 + 8t - t^2$.

Step 2. Greatest velocity. $a = 0$ at $t = 4\ \text{s}$; $v = 3\ \text{m/s} + 32\ \text{m/s} - 16\ \text{m/s} = 19\ \text{m/s}$.

Step 3. Position. $x = 3t + 4t^2 - \dfrac{t^3}{3}$, so $x(4\ \text{s}) = 12\ \text{m} + 64\ \text{m} - 21.33\ \text{m} = 54.67\ \text{m}$.