a) $$4^{11} \cdot 4^{-9} = 4^{11 + (-9)} = 4^2 = 16$$
б) $$6^{-5} \cdot 6^{-3} = 6^{-5 + (-3)} = 6^{-8} = \frac{1}{6^8} = \frac{1}{1679616}$$
в) $$(2^{-2})^3 = 2^{-2 \cdot 3} = 2^{-6} = \frac{1}{2^6} = \frac{1}{64}$$
Ответ: a) 16; б) $$\frac{1}{1679616}$$; в) $$\frac{1}{64}$$