Under constant acceleration, we have
[tex]v^2-{v_0}^2 = 2ax[/tex]
where [tex]v[/tex] is final velocity, [tex]v_0[/tex] is initial velocity, [tex]a[/tex] is acceleration, and [tex]x[/tex] is distance.
Solving for [tex]x[/tex] gives
[tex]x = \dfrac{v^2-{v_0}^2}{2a}[/tex]
Then if the car starts with speed 25 m/s and acceleration -7.0 m/s², and comes to a rest (so that [tex]v=0[/tex]), we have
[tex]x = \dfrac{-\left(25\frac{\rm m}{\rm s}\right)^2}{2\left(-7.0\frac{\rm m}{\mathrm s^2}\right)} \approx \boxed{45\,\mathrm m}[/tex]
