Since each team only plays against every other team once, there are only 10 games played in total.

Teams :

1 vs 2
1 vs 3
1 vs 4
1 vs 5
2 vs 3
2 vs 4
2 vs 5
3 vs 4
3 vs 5
4 vs 5

Since 2 games were played at the same time,

10 ÷ 2 = 5

There is a minimum of 5 sessions.

Now, 3 hours = 3 × 60 min = 180 min

Maximum amount of time for each game would be the maximum amount of time for each session.

180 ÷ 5 sessions = 36 minutes per session

So each game can only last at most 36 minutes.

As for the teaming roster, there are many possibilities.

(Note that this is not required by the question)

Here is one of them :

1st session : 1 vs 2 , 3 vs 4
(36 minutes)

2nd session : 2 vs 3 , 4 vs 5
(36 minutes)

3rd session : 1 vs 4 , 3 vs 5
(36 minutes)

4th session : 1 vs 5 , 2 vs 4
(36 minutes)

5th session : 2 vs 5 , 1 vs 3
(36 minutes)