1. The problem statement, all variables and given/known data How many contestants have on one chess tournament, if every person have played only one game with all of the other contestants separately, and there are 210 games played. This problem should not be solved by variations, permutations or combinations. This problem should be solved by using the quadric equation. (we should put some condition, and out of there make some quadric equation). 2. Relevant equations 3. The attempt at a solution I have no idea. x- the number of players I really don't know.