Combinations without repetition

Find out how many different ways you can choose k items from n items set. With/without repetition, with/without order.

Calculation:

C_{k} (n) = (\binom{n}{k}) = \frac{n!}{k! (n - k)!} n = 11 k = 3 C_{3} (11) = (\binom{11}{3}) = \frac{11!}{3! (11 - 3)!} = \frac{11 \cdot 10 \cdot 9}{3 \cdot 2 \cdot 1} = 165