How can I find the average speed of two trains?

: How can I find the average speed of two trains?
Two trains drive towards each other in two separate tracks with a constant speed. Train A is 200 m long and train B is 400 m long. When the trains pass each other it takes 5 seconds from the fronts of the trains meet to the ends of the trains pass. If the trains drive in the same velocity, but in the same direction, it takes 15 seconds for train A to pass by train B. What is the average speed of train A and train B?
PS. I think the meaning is to find two different average speeds.

Answers and Views:

Answer by listen to me
400+200/x= 5

600/5=120m/s

Answer by EASY TO UNDERSTAND
Two trains drive towards each other in two separate tracks with a constant speed. Train A is 200 m long and train B is 400 m long. When the trains pass each other it takes 5 seconds from the fronts of the trains meet to the ends of the trains pass. If the trains drive in the same velocity, but in the same direction, it takes 15 seconds for train A to pass by train B.
The average speed of train A is given by (200 + 400)[1/5 + 1/15)/2 m/s = 80 m/s ANSWER
and train B average speed given by (200 + 400)[1/5 — 1/15]/2 m/s = 40 m/s ANSWER