A female soccer club has 23 players. The strength of each player is a positive integer assigned to the player based on her
performance in the last 3 seasons. It turns out that leaving any player aside, the remaining 22 players can be divided into two teams of 11 so that the sum of strengths of all players in each team is the same. Prove
that all players have the same strength.
Only one solution was received, form Yuqiao Huang. His solution is essentially the same as ours. The
solution and some additional remarks are
contained in the following link Solution