The question does not give any frictional forces like air resistance so we have to assume that these are negligible.
The deceleration, a, of the car can be found using:
v v = u u + 2 a s
where the u is the initial speed of 8.9 m/s and v = o as the car comes to a stop.
The distance, s, it slows down over is 12 m.
So, 0 = u x u + 2 x a x 12
A bit of maths gives:
a = - 3.3 m/ss (the negative sign just tells us that the car is decelerating).
If friction is zero, then the braking force, F, is given by F = ma as this is the only horizontal force acting on the car, which we assume is on a horizontal road:
F = m a
So, F = 800 x - 3.3 = - 2640 N.
(Again the negative sign just tells us that the car is decelerating).
Note that your spelling of braking force in the question was wrong.