Hello!
[tex]\large\boxed{-2m/s^{2} }[/tex]
Find the acceleration using the formula a = (vf - vi) / t where:
vf = final velocity
vi = initial velocity
t = time
Plug in the points above:
vf = +10 m/s
vi = +20 m/s
t = 5 sec
(10 - 20) / 5 = -10 / 5 = -2 m/s²
