Ответ:

  1. \(2.5^{-2/3}=\dfrac{1}{\sqrt[3]{(2.5)^2}}\).
  2. \(\left(\dfrac{1}{9}\right)^{-1/2}=\dfrac{1}{\sqrt{1/9}}=3\).
  3. \(0.5^{0.5}=0.5^{1/2}=\sqrt{0.5}\).