a) $$\left(\frac{1}{6}x^{-4}y^3\right)^{-1}$$ = $$\left(\frac{1}{6}\right)^{-1} * (x^{-4})^{-1} * (y^3)^{-1}$$ = 6x4y-3 = $$\frac{6x^4}{y^3}$$.
б) $$\left(\frac{3a^{-4}}{2b^{-3}}\right)^{-2} * 10a^{-7}b^3$$ = $$\frac{(3a^{-4})^{-2}}{(2b^{-3})^{-2}} * 10a^{-7}b^3$$ = $$\frac{3^{-2} * a^{8}}{2^{-2} * b^{6}} * 10a^{-7}b^3$$ = $$\frac{4}{9} * a^{8} * b^{-6} * 10a^{-7}b^3$$ = $$\frac{40}{9} * a^{8-7} * b^{-6+3}$$ = $$\frac{40}{9} * a^1 * b^{-3}$$ = $$\frac{40a}{9b^3}$$.
Ответ: а) $$\frac{6x^4}{y^3}$$, б) $$\frac{40a}{9b^3}$$.