\[\frac{7x^{4}y^{13}}{18m^{2}n^{5}}\ :\frac{35x^{5}y^{8}}{33m^{4}n^{8}}\ :\frac{11y^{2}n^{9}}{9xm^{4}} =\]
\[= \ \frac{7x^{4}y^{13} \cdot 33m^{4}n^{8} \cdot 9xm^{4}}{18m^{2}n^{5} \cdot 35x^{5}y^{8} \cdot 11y^{2}n^{9}} =\]
\[= \frac{3y^{3}m^{6}}{10n^{6}}\]