Question

How do you evaluate `7"C"_2`?

Answer 1

`21`

Explanation:

`nCr=((n),(r))=(n!)/(r!(n-r)!)`

`7C_2=((7),(2))=(7!)/(2!(7-2)!)=(7!)/(2!*5!)=(5040)/(2*120)=5040/240=21`