Answer
$\frac{y^{12}}{3x^{8}}$
Work Step by Step
$$\frac{10x^{4}y^{9}}{30x^{12}y^{-3}}$$
Group factors with like bases:
$$=(\frac{10}{30}))(\frac{x^{4}}{x^{12}})(\frac{y^{9}}{y^{-3}})$$
$$=\frac{1}{3}x^{(4-12)}y^{(9-(-3))}$$
$$=\frac{1}{3}x^{-8}y^{(9+3)}$$
$$=\frac{1}{3}x^{-8}y^{12}$$
Write as a fraction, move the base with the negative exponent to the other side of the fraction, and make the exponent positive:
$$=\frac{y^{12}}{3x^{8}}$$
