Question 594161
C(n,r) = (n!)/(r!(n-r)!)


C(18,4) = (18!)/(4!*(18-4)!)


C(18,4) = (18!)/(4!*14!)


C(18,4) = (18*17*16*15*14!)/(4!*14!)


C(18,4) = (18*17*16*15)/(4!)


C(18,4) = (18*17*16*15)/(4*3*2*1)


C(18,4) = (73440)/(24)


C(18,4) = 3060


So there are <font color="red">3,060</font> different groups.