#16! =1*2*3*4*5*6*7.......*16#
#9! =1*2*3*4*5*6*7...*9#
#7! =1*2*3*4*5*6*7#
#(16!)/(9!*7!)=#
#(1*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16)/((1*2*3*4*5*6*7*8*9)(1*2*3*4*5*6*7))#
The number that equal other cancel out!
#rarr=(10*11*12*13*14*15*16)/(1*2*3*4*5*6*7)#
#7# and #14# cancel out ,#6# and #12# cancel out ,#5# and #10# cancel out!
#rarr=(2*11*2*13*2*15*16)/(1*2*3*4*1*1*1)#
Now #4# and #14# cancel out,#2# and #2# cancel out, #3# and #15# cancel out!
#rarr=(2*11*1*13*2*5*4)/(1*1*1*1*1*1*1)#
#rarr=2*11*1*13*2*5*4#
#rarr=22*26*20#
#rarr=440*26#
#rarr=11440#