let we have seven men as a,b,c,d,e,f,g
we have to pick 2 men to form a pair
no. of ways to pick 2 men from 7 = C(7,2)
=21 pairs
after picking 2 men from 7 people we are left with 5 men's , again we need one more pair to play
so it can be done in C(5,2) = 10 ways
total = 21*10
=210
now if ab is picked and played against cd similarly cd is picked and plays against ab
order does not matter for each pair
so total games played = 210/2
=105