Question

How many league matches were played, write an algebraic expression to
denote the number of
league matches between the teams, if the number of teams is n.

Answer 1

look at the pattern.

Two teams A, B
one game: C(2,2) = 1 ---> from 2 choose 2 for a game

AB
Three teams A,B,C
AB, AC, BC --- three games , C(3,2) --> from 3 choose 2 for a game

Four teams A,B,C,D
AB, AC, AD, BC, BD, CD - 6 games, C(4,2) ---> from 4 choose 2

...

n teams ---- C(n,2) , from n choose two

C(n,2) = n!/(2!(n-2)!)
= n(n-1)(n-2)(n-3)!/(2(n-2)(n-3)!_
= n(n-1)/2

Answer 2

And now "Sweety" or whatever s/he is called is banned for posting filth.