Still not a complete answer. Here we go then.
If a body is moving long the x-axis, starting at initial position \( x_0 \), with initial velocity \( v_0 \) and accelerating at a constant rate of \( a \), then its position at time t, x(t), is given by
\[ x(t) = x_0 + v_0t + \frac{1}{2}at^2 \]
and it's velocity at time t, v(t) is given by
\[ v(t) = v_0 + at \]
Now we're told this about the first toy car:
"one toy car is set rolling on a straight track with initial position 13.5 cm, initial velocity -4.2 cm/s, and constant acceleration 2.60 cm/s^2".
Hence for that first car, \( x_0 = 13.5 cm \), \( v_0 = 4.2 cm/s \) and \( a = 2.60 cm/s^2 \). Therefore its velocity is
\[ v_1(t) = 4.2 + 2.60t \]
and position
\[ x_1(t) = 13.5 + 4.2t + \frac{1}{2}2.60t^2 = 13.5 + 4.2t + 1.30t^2 \]
Now, what about the second car: "another toy car is set rolling on an adjacent track with initial position 8.5 cm, initial velocity 5.20 cm/s, and constant zero acceleration." Hence its velocity, is
\[ v_2(t) = 5.20 \]
\[ x_2(t) = 8.5 + 5.2t \]
That's the set up.