we divided by 2 bcz say the case when two teams B and C have 5 and 5 player each is similar to saying C and B have 5 and 5 player each bcz there are three teams and it is not mentioned which team get 2, 5,5 players (i.e. question doesn’t say like team A should have 2 , B should have 5 and C should have 5 instead its says 3 teams can have 2,5,5 players each)