Question 1205092
<pre>

{{{(nCk)(kCr) = (nCr)(n-r)C(k-r)}}}

{{{(n!/(k!(n-k)!))*(k!/(r!(k-r)!))}}}{{{""=""}}}{{{(n!/(n!(n-r)!))*((n-r)!/(  (k-r)!((n-r)-(k-r))!   ))}}}

{{{(n!/(cross(k!)(n-k)!))*(cross(k!)/(r!(k-r)!))}}}{{{""=""}}}{{{(n!/(r!(cross(n-r))!))*((cross(n-r))!/(  (k-r)!(n-r-k+r)!   ))}}}

{{{n!/((n-k)!r!(k-r)!)}}}{{{""=""}}}{{{n!/(r!(k-r)!(n-k)!))}}}

Those are the same except for the order of factors in the denominator.

Your notation in the second one is incompatible with this site, making it
so garbled, I can't make it out.

Edwin</pre>