\[\frac{\sqrt[4]{x^{4}y^{5}}}{3x\sqrt[4]{81y}} = \frac{\sqrt[4]{x^{4}y^{4} \cdot y}}{3x\sqrt[4]{3^{4}y}} =\]
\[= \frac{|x| \cdot |y| \cdot \sqrt[4]{y}}{3x \cdot 3\sqrt[4]{y}} = \frac{|x| \cdot |y|}{9x}\]
\[x = - \frac{5}{9};\ \ \ y = 18:\]
\[\frac{|x| \cdot |y|}{9x} = - \frac{\text{xy}}{9x} = - \frac{y}{9} =\]
\[= - \frac{18}{9} = - 2.\]