Let $d_1, t_1, v_1$ be distance, time, and speed of the train before stopping.
Let $d_2, t_2, v_2$ be the distance, time, and speed of the train while it was stopped. (Hint: If the train is stopped then $v_2 = 0$. And $d_2 = .....$?)
Let $d_3, t_3, v_3$ be the distance, time and speed of the train when it picked up speed. (Hint: The question specifically tells you that $d_3 = 99$. It also tells you something about $v_3$...)
Let $d = d_1 + d_2 + d_3$ be total distance and $t=t_1 + t_2 + t_3$ be total time.
The question says the train made up lost time:
That means $d = v_1*t= v_1*t_1 + v_2*t_2 + v_3*t_3$.
Can you set that up?
Can you solve it?
Since the train stopped it did $99 = (v + 20)t$ to make up for lost time.
But what if it hadn't stopped and had been going at the original speed for the lost $12$ minutes. Then you'd have $99=v(t+12)$.