physics--please provide equations?

Question

. Two trains face each other on adjacent tracks. They are initially at rest 45 m apart. The train on the left accelerates rightward at 1.4 m/s2. The train on the right accelerates leftward at 2.7 m/s2. How far does the train on the left travel before the two trains pass?

Answer 1

d = (0.5) aT * t * t

you've got d = 45 m

you've got total acceleration (aT) as a1 + a2. you can solve for time. once you have this, solve back in the equation

dL = (0.5) aL * t *t

since you now have t from the first part, and you know aL as a given, you can solve for dL, distance the left train travelled