\[5x^{2}y^{3} = - 7\]
\[x^{2}y^{3} = - \frac{7}{5}\]
\[5x^{4}y^{6} = 5 \cdot \left( x^{2}y^{3} \right)^{2} = 5 \cdot \left( - \frac{7}{5} \right)^{2} =\]
\[= 5 \cdot \frac{49}{25} = \frac{49}{5} = 9,8.\]