Recall that
[tex]{v_f}^2-{v_i}^2=2a\Delta x[/tex]
where [tex]v_i[/tex] and [tex]v_f[/tex] are initial and final velocities, respectively; [tex]a[/tex] is acceleration; and [tex]\Delta x[/tex] is the net displacement, or distance if the object is moving in a single direction.
The car has initial speed 20 m/s and acceleration -3.25 m/s². It comes to a stop, so it has 0 final speed. Then
0² - (20 m/s)² = 2 (-3.25 m/s²) ∆x
∆x = (20 m/s)² / (7.5 m/s²) ≈ 53.3 m
