Ответ:

  1. \(8^{-3}\cdot\left(\dfrac12\right)^3=\dfrac{1}{8^3}\cdot\dfrac18=\dfrac{1}{4096}\).
  2. \(25^{-3}\cdot15^4=5^{-6}\cdot(3\cdot5)^4=\dfrac{3^4}{5^2}=\dfrac{81}{25}\).
  3. \(6^{-4}:3^{-6}=\dfrac{3^6}{6^4}=\dfrac{729}{1296}=\dfrac{9}{16}\).
  4. \(\left(\dfrac34\right)^{-5}:\left(-\dfrac43\right)^8=\left(\dfrac43\right)^5:\left(\dfrac43\right)^8=\left(\dfrac34\right)^3=\dfrac{27}{64}\).
  5. \(\dfrac{2^{-5}\cdot16^2}{8^4}=\dfrac{\frac1{32}\cdot256}{4096}=\dfrac1{512}\).

Ответ: \(\dfrac{1}{4096};\ \dfrac{81}{25};\ \dfrac{9}{16};\ \dfrac{27}{64};\ \dfrac{1}{512}\).