two dimensional acceleration question

[F.B]

My book stinks it doesnt explain or show you how to do enough examples. But anyways i have another problem now. I figured out how to do my other question. Anyways my question is.......

 

A car with a velocity of 25 m/s [E] changes its velocity to 25 m/s in 15s. Calculate the car's average acceleration.

 

How do i start this question off. I dont know what to do.

[timo]

[E] is east and is south?

In that case start writing the velocities as a vector, for example as (vNorth, vEast). Then, calculate the difference between those vectors. Average accelleration times time is the change in velocity. Solve for average acceleration.