Sarah has 6 friends who are available to go with her to the movies, but she only has 2 extra tickets. How many different choices does Sarah have for which 2 friends to invite.

Relax

Respuesta :

Person 1: 5 choices to pair with
Person 2: 4 choices
Person 3: 3 choices
Person 4: 2 choices
Person 5: 1 choice

Therefore, she has 15 choices for which 2 friends to invite