A train with a velocity of 45.1 m/s must come to an emergency stop in 10.6 s. How far did it travel during this time?

i tried to use the x=1/2at^2+vit+xi equation but that did not work..

If you find the acceleration first, using a = (Vf - Vi) / t, then you can find displacement by d = Vi*t + (1/2)a*t^2