Watercraft with velocity east and acceleration south

[F.B]

I have no idea how to do these questions. My teacher did not explain anything.

Anyways my question is:

A watercraft with an initial velocity of 6.4 m/s [East] undergoes an average acceleration of 2.0 m/s^2 [South] for 2.5 s. What is the final velocity of the watercraft?

This are going in different directions. How do i do these types of questions? Please help me.

 

[Leong]

use vector notation in 2D ie i and j.