Question 1125717


{{{nCr = n!/(r! (n-r)!)}}} 

{{{6C3 = 6!/(3! (6-3)!)}}} 

{{{6C3 = 6!/(3! *3!)}}}

{{{6C3 = (6*5*4*3*2*1)/((3*2*1)(3*2*1))}}}

{{{6C3 = (cross(6)*5*4*cross(3*2*1))/(cross((3*2*1))(cross(3*2*1)))}}}

{{{6C3 =20}}}