A particle is moving along the x-axis with constant deceleration 5ms-2. At time=0, the particle passes through the origin o with velocity 12ms-1 in the positive direction. At time t secounds the particle passes through the point A with x-coordinates 8. Find the values of t.

Any help?

I know the formula that is used is s=ut+1/2at^2 but I keep getting the wrong answer.