Question 427273
{{{c(18,r)=c(18,r+2)}}}
<==> {{{(18!)/((18-r)!r!) = (18!)/((16-r)!(r+2)!)}}}
<==> {{{1/((18-r)!r!) = 1/((16-r)!(r+2)!)}}}
<==> {{{1/((18-r)(17 - r)) = 1/((r+1)(r+2))}}}
<==> {{{(18-r)(17 - r)=  (r+1)(r+2)}}}
<==> {{{306-35r + r^2 = r^2 + 3r + 2}}}
<==> 304 = 38r ==> r = 8.