Acar slows down uniformly from a speed of 30.0 m/s to rest in 7.20 show far did it travel in that time?

When acceleration is constant, the average velocity is given by

where and are the final and initial velocities, respectively. By definition, we also have that the average velocity is given by

where are the final/initial displacements, and are the final/initial times, respectively.

Take the car's starting position to be at . Then

So we have

You also could have first found the acceleration using the equation

then solve for via

but that would have involved a bit more work, and it turns out we didn't need to know the precise value of anyway.