Question 669715
C(n,r) = (n!)/(r!(n-r)!)


C(6,4) = (6!)/(4!*(6-4)!)


C(6,4) = (6!)/(4!*2!)


C(6,4) = (6*5*4!)/(4!*2!)


C(6,4) = (6*5)/(2!)


C(6,4) = (6*5)/(2*1)


C(6,4) = (30)/(2)


C(6,4) = 15


So there are 15 ways.