For an uniformly accelerated motion, the final velocity is given by:
[tex]v_f = v_i +at[/tex]
where vi is the initial speed, a is the acceleration, and t the time interval.
In our problem, [tex]v_i=65 m/s[/tex], [tex]a=-3.8 m/s^2[/tex] (with negative sign, because the car is decelerating), and [tex]t=12 s[/tex]. Substituting,
[tex]v_f = 65 m/s+(-3.8 m/s^2)(12 s)=19.4 m/s[/tex]
