Answer
$$\frac{-10x^{4}y^{3}}{-40x^{-2}y^{6}}=\frac{x^{6}}{4y^{3}}$$
Work Step by Step
$$\frac{-10x^{4}y^{3}}{-40x^{-2}y^{6}}$$
Recall the quotient rule: $\frac{a^{m}}{a^{n}}=a^{m-n}$ and $\frac{a^{n}}{a^{m}}=\frac{1}{a^{m-n}}$
Thus,
$$\frac{-10x^{4}y^{3}}{-40x^{-2}y^{6}}$$ $$\frac{-10}{-40}\cdot \frac{x^{4-(-2)}}{y^{6-3}}$$ $$=\frac{x^{6}}{4y^{3}}$$