I believe this problem ask to express the velocity of the first car and second car in terms of t.
The general expression for the velocity is given as:
v = v0 + a t
where v is the velocity, v0 is the initial velocity, a is acceleration, t is time
a. velocity equation for the first car
v = 30 – 6 t
b. velocity equation for the second car
v = 24 – 6 t
We can see that the acceleration is negative because both cars are slowing down (deceleration).
