Answer :

wrevents
Hi Kally 

  Here is what I was able to come up!

  4/x-2/x^2y^3

Double check it ok...
[tex]\frac{4y}{xy}-\frac{2x}{xy^3}=\frac{4}{x}-\frac{2}{y^3}\\\\\\\frac{4y}{xy}-\frac{2x}{xy^3}=\frac{4y^3}{xy^3}-\frac{2x}{xy^3}=\frac{4y^3-2x}{xy^3}[/tex]