A car starts from rest and travels for 6 seconds with a uniform acceleration of -2m/s. What is the final velocity?

Yep good and what do you think.
Rather than simply copying your homework show us what you have tried so far.

https://www.askmehelpdesk.com/math-sciences/announcement-font-color-ff0000-u-b-read-first-expectations-homework-help-board-b-u-font.html

AS I worked it out I received -12m/s for the answer

-12m/s

Formula is v = u + at

V = final velocity

u = initial velocity

a = acceleration

t = time

first of all a car cannot have acceleration of -2m/s^2 as it is starting from rest. So please check question

How could it have a negative acceleration if it is already at rest?

Yes dats what I asked

Of course velocity can be negative! Speed cannot be negative but velocity and accelerations can be negative. It depends on which direction you consider positive.

For example, if forward is positive, backward is negative and negative velocity means car moving backwards!

Semantics I suppose, with unclear nomenclature leading to supposition that negative velocity equates to slowing down as opposed to going backward

Yes I know that the velocity and acceleration can be negative but for information of you all, here the body is starting from rest... so pease check it out

OK man.. you say that negative velocity means moving back but when the body is moving then the force acting on it is also acting backwards so the car moves in the direction of force... so wt will u say it JITENJI