Permutations have a repeated pattern. it is like 16!. that means it is 16*15*14*13*12*11*10*9*8*7*6*5*4*3*2*1. and once you get that answer you have to do the bottom. so if you have 16!/5! then you can eliminate the 5*4*3*2*1 from both equations and you then get your answer
