An object is moving along the x axis at t 54 s the object

Question

Problem: An object is moving along the x axis. At t = 5.4 s, the object is at x = +3.0 m and has a velocity of +5.4 m/s. At t = 8 s, it is at x = +9.0 m and its velocity is -1.0 m/s.

Part A: Find the average acceleration during the time interval 5.4 s ? t ? 8 s.

m/s²

Please explain the equations and steps are used to get the answer. Thanks!