consider the direction towards the wall as negative and away from the wall as positive.
m = mass of the car colliding with the brick wall = 1500 kg
v₀ = initial velocity of the car towards the wall = - 20 m/s
v = final velocity of the car = 0 m/s
t = time taken by car to come to rest after collision = 0.80 s
F = force sustained by the car
using impulse-change in momentum
F t = m (v - v₀ )
inserting the values
F (0.80) = (1500) (0 - (- 20))
F (0.80) = 30,000
F = 30000/0.80
F = 37500 N