[tex]\frac{-18z^{7}y^{5}-9z^{9}y^4+18z^6y^8}{9zy^{2} }= -2z^6y^3-z^8y^2+2z^5y^6[/tex]
When variables with exponents are divided by each other, you subtract the exponents.
For example:
[tex]\frac{x^2}{x^1} = x^{2-1} =x^1[/tex]
[tex]\frac{x^5}{x^3} =x^{5-3} = x^2[/tex]
