Answer:
There are 7 teams in the league
Step-by-step explanation:
Given that the number of games is given by:

The equation will be used to determine the number of games. As we already know, that 21 games are scheduled which means G(n) is 21 so we have to find n when G(n) is 21
Putting this mathematically

Multiplying equation by 2

As the number of teams cannot be negative, the number of teams in league are 7.
Hence,
There are 7 teams in the league