n=17 r=4 formula ncr=n!/(n-r)!r! in this question we combination you need to combinate 17 participants in groups of four so you make a combination: Combination of 17, 4 = 17c4=17!/(17-4)4! 17c4=17*16*15*14*13!/13!*4! 13! cancel out 17c4=17*16*15*14/4! 17c4=17*16*15*14/4*3*2 17c4=17*14*5*2 17c4=2380 answer is 2380