Question 105139
I assume you mean like the following:
{{{((n^2-n-20)/2n^2)((n^2+5n)/(n^2-25))}}}
Let's do some manipulation on both before we multiply. 
{{{(n^2-n-20)/2n^2=((n-5)(n+4))/2n^2}}}
{{{(n^2+5n)/(n^2-25)=(n(n+5))/((n+5)(n-5))=n/(n-5)}}}
That simplifies some of the multiplication
{{{((n^2-n-20)/2n^2)((n^2+5n)/(n^2-25))=((cross((n-5))(n+4))/2n^cross(2))*(cross(n)/cross((n-5)))}}}
{{{((n^2-n-20)/2n^2)((n^2+5n)/(n^2-25))=(n+4)/2n}}}