Question 356062
I am not really sure what part this falls under, but i had this question on a test, never seen anything like this before: you are given 
<pre>
Given:
{{{system(x=5y,y=sqrt(5))}}}

Find
{{{(x*sqrt(5))/(5y)}}}

Substitute {{{sqrt(5)}}} for {{{y}}}

{{{(x*sqrt(5))/(5sqrt(5))}}}

Cancel the {{{sqrt(5)}}}s

{{{(x*cross(sqrt(5)))/(5cross(sqrt(5)))}}}

{{{x/5}}}

Substitute {{{5y}}} for {{{x}}}

{{{(5y)/5}}}

Cancel the {{{5}}}'s

{{{(cross(5)y)/cross(5)}}}

All that's left is {{{y}}}

Edwin</pre>