Acceleration is change in velocity over time --> [tex]a = \frac{Δv}{t}[/tex]
Δv or change in velocity equals the Final velocity minus the initial velocity
Our initial velocity here is 60m/s while our final velocity is 0 m/s
The time interval is 85 seconds so...
[tex]a = \frac{0-60}{85}[/tex]
[tex]a = \frac{-60}{85}[/tex]
[tex]a = -0.706[/tex]
The negative is there to indicate that the train in slowing down or decelerating
