\[\frac{\left( 25x^{3} \right)^{2} \bullet \left( 5x^{5} \right)^{3}}{\left( 125x^{8} \right)^{2}} = - 160\]
\[\frac{5^{4}x^{6} \bullet 5^{3}x^{15}}{5^{6}x^{16}} = - 160\]
\[\frac{5^{7}x^{21}}{5^{6}x^{16}} = - 160\]
\[5x^{5} = - 160\ \ \ \ \ |\ :5\]
\[x^{5} = - 32\]
\[x = - 2.\]