SOLUTION: in how many ways can 2 co-chairs be selected from a club of 20 students?

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Question 306621: in how many ways can 2 co-chairs be selected from a club of 20 students?
Answer by dabanfield(803) About Me  (Show Source):
You can put this solution on YOUR website!
C(20,2) = 20!/((20-2)!*2!) = 20!/(18!*2!)