$2a^{-5}b^2 * 3a^{-2}b^{-5} = (2 * 3)a^{-5 - 2}b^{2 - 5} = 6a^{-7}b^{-3}$

$(\frac{1}{2}mn^{-3})^{-2} = (\frac{1}{2})^{-2}m^{-2}n^{-3 * (-2)} = 2^2m^{-2}n^6 = 4m^{-2}n^6$

$\frac{3,6a^2b}{0,9a^3b^{-3}} = \frac{4b^{1 - (-3)}}{a} = \frac{4b^{1 + 3}}{a} = \frac{4b^{4}}{a}$

$0,8a^{-6}b^8 * 5a^{10}b^{-8} = (0,8 * 5)a^{-6 + 10}b^{8 - 8}= 4a^4b^0 = 4a^4$

$\frac{25x^{-3}}{y^{-4}} * \frac{y^{4}}{5x^{-7}} = \frac{25y^4}{x^3} * \frac{x^7y^{4}}{5} = \frac{5y^4}{1} * \frac{x^4y^{4}}{1} = 5x^4y^8$

$28c^3d^{-2} * (2cd^{-1})^{-2} = 28c^3d^{-2} * \frac{c^{-2}d^2}{2^2} = \frac{28c^{3 - 2}d^{-2 + 2}}{4} = \frac{7c^{1}d^{0}}{1} = 7c$