A car slows from 25m/s to 5m/s at 2m/s^2 how many seconds takes it

Kinetics
Vi = 25
Vf = 5
a = -2 (makes the math work because you are slowing down)
t = ?

So you don't know d or displacement so use Vf = Vi + at

5 = 25 - 2t
-20 = -2t
t = 10seconds

Time taken is 10s use v=u+at
Accelaration=-2m/s^2 means that velocity will be decreased by 2 m/s every second.

Change = 20m/sec.
Time = (v/a) = 20/2, = 10 secs.