Pt A is t = 0 there are 9 pictures (red dots) to where he is now
9 pictures / 20 pictures/s = .45 s
He is going 18 m/s from t = 0 to t = .45 s distance = .45 x 18 = 8.1 m
Then he begins deccelerating to 2.4 m/s from .45 to t = 3 sec
then he instantly stops (I do not know why they tell you he stays still until t = 4 sec)
vf = v0 + a t t is 3 - .45 = 2.55s
2.4 = 18+ a (2.55)
results in a = - 6.18 m/s^2
how far did he travel while braking (which we will add to the 8.1 m above)
xf = x0 + vo t + 1/2 a t^2
xf = 18 (2.55) + 1/2 (-6.18) (2.55^2)
= 26.01 m
Add the 8.1 distance = 34.11 m