1. The number of possible rosters is equal to the number of choices multiplied by each other. So,

a. if there were only two players (A, B) on the roster and if only one player makes a team, there would be just 2 possible teams (A and B).

b. If there were only three players (A, B, C) on the roster and if two players make a team, there would be just 6 possible teams (AA, BA, CA, AB, AC, BC).

c. If there are 5 players (A, B, C, D, E) on the roster and if three players make a team, there would be 10 possible teams (ABC, ABD, ABE, ACD, ACE, BCD, BCE,CBD, CBE, CDE).

2. You can try more examples and you will see that if there are n players on the roster and if q players make a team, there would be  possible teams.

3. If there are 18 players (A, B, C…R) on the roster and 11 players make a team, then the number of choices include the following:

4.   = 31,824