The word team should make you think combination.
The question is asking for the following fraction:
(total number of good teams)/(total number of possible teams)
Let's determine each part of this fraction separately.
To determine the total number of possible teams, we need to determine how many combinations of 5 can be made from 9 choices:
(9*8*7*6*5)/(1*2*3*4*5) = 126 total possible teams
A good team will consist of John and Peter put together with 3 other players. Since we know that John and Peter have to be included in a good team, our only concern is the number of ways we can choose the 3 other players from the 7 we have left.
So we need to determine how many combinations of 3 can be made from 7 choices:
(7*6*5)/(1*2*3) = 35 good teams.
So (good teams)/(total teams) = 35/126 = 5/18.
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