To solve for the distance covered.
a) Solve for distance before applying the brake which is during the reaction time.
reaction time = 1.5 seconds, and the speed is 20m/s.
Distance = 20m/s * 1.5s = 30 m.
b) Distance covered during deceleration.
v² = u² + 2as
Deceleration, a = -7 m/s²
We would assume it decelerates to a stop. v = 0, u = 20 m/s
v² = u² + 2as
0² = 20² + 2*(-7)s
0 = 20*20 - 14s
0 = 400 - 14s
14s = 400
s = 400/14
s ≈ 28.57 m
Hence distance covered = distance covered during reaction time + distance covered during deceleration
= 30 m + 28.57 m = 58.57 m
So the car traveled ≈ 58.57 m
Hope this explains it.
