I have a High school physics exam study guide? cant solve

[baustin]

Homework Statement

A car moving with an initial velocity of 25 m/sec north has a constant acceleration of 3 m/sec2 south. After 6 seconds its velocity will be?

7 m/sec north

7 m/sec south

43 m/sec north

20 m/sec north

20 m/sec south

Homework Equations

Im not sure, but X-Xo=0.5( V + Vo) (t)

The Attempt at a Solution

X=
V= 25/3 (6)
Not even sure where to go from here...

 

[Chestermiller]

What are some of the other SUVAT equations, and which one of these involves only velocity and acceleration?