a) $$\frac{3^{27}}{9^{12}} = \frac{3^{27}}{(3^2)^{12}} = \frac{3^{27}}{3^{24}} = 3^{27-24} = 3^3 = 27$$.
б) $$\frac{125^{11}}{25^{17}} = \frac{(5^3)^{11}}{(5^2)^{17}} = \frac{5^{33}}{5^{34}} = 5^{33-34} = 5^{-1} = \frac{1}{5} = 0.2$$.
Ответ: a) $$27$$; б) $$0.2$$