Superhero ScrambleDiscrete Mathematics Level 4
In a certain online game, two players, red and blue, play against each other using teams of heroes. There are seven heroes available to each player. Before a game, each player chooses three of the seven heroes to form a team. The two players create their teams independently, so it is possible that the players may pick some of the same heroes. How many ways are there for the two players to form their teams so that the teams have exactly one hero in common?