The first train runs at v1 = 36km / h. after t = 30 minutes, the second train departed from the same station in the same

The first train runs at v1 = 36km / h. after t = 30 minutes, the second train departed from the same station in the same direction with a speed of v2 = 72 km / h. after what time t2 after the exit of the first train will it catch up with the second?

To answer the question of the problem, you need to solve the following equation.
36 * 0.5 + 36 * t = 72 * t
36t = 18
t = 0.5 (h)
Answer: in 30 minutes the trains will meet