I assume you mean 20 m/s.
In the first 0.80 seconds, the car travels:
20*0.80 = 16 m
During the period of deceleration, you can calculate the distance travelled using:
[tex] v^{2} = u^{2} + 2as[/tex] where s is the distance travelled, v is the final speed (0), u is the initial speed (20 m/s), and a is the acceleration (-7.0 m/s^2).
This gives:
2*7.0s = 20^2
14.0s = 400
s = 400/14 m
The total distance the car travels is:
16 + 400/14 = 44.6 m (3 s.f.)
