Ответ:

  1. \(0.5\sqrt{1600}-\frac{1}{3}\sqrt{36}=0.5\cdot40-\frac{1}{3}\cdot6=20-2=18\).
  2. \(\sqrt{0.25\cdot81}=\sqrt{20.25}=4.5\).
  3. \(\sqrt{6^2\cdot2^8}=6\cdot16=96\).
  4. \(\sqrt{20}\cdot\sqrt{5}-\frac{\sqrt{63}}{\sqrt{7}}=\sqrt{100}-\sqrt{9}=10-3=7\).