An object moving at 31m/s takes 6s to come to a stop. What is the object's acceleration?

31m/s is the velocity of the object and in 6 seconds the object stops so its velocity is then 0 m/s.

acceleration formula is a = Δv / Δt = (vf - v i) / (tf - t i)

= (final velocity - initial velocity) / (final time - intial time)

kinda like the slope formula right?

so subsitute the values

(0 - 31) / (6 - 0)

The answer should be negative as the velocity is decreasing