We need to find the average acceleration, this is given by the next formula:
[tex]a=\frac{vf-vi}{t}[/tex]Where:
vf = final velocity
vi = initial velocity
t = time.
Hence, we can replace using:
vf = 22 m/s
vi = 4 m/s
t = 3s
Then:
[tex]\begin{gathered} a=\frac{22\frac{m}{s}-4\frac{m}{s}}{3s} \\ Then \\ a=6\frac{m}{s^2} \end{gathered}[/tex]Hence, the average acceleration is 6 m/s²