\[\frac{16x^{2}y^{8}}{15m^{4}n^{8}}\ :\left( - \frac{8x^{3}y^{5}}{35m^{6}n^{7}} \right) =\]
\[= - \frac{16x^{2}y^{8} \cdot 35m^{6}n^{7}}{15m^{4}n^{8} \cdot 8x^{3}y^{5}} =\]
\[= - \frac{14y³m²}{3nx}\]