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) \(\sqrt{6^2\cdot2^8}=\sqrt{36\cdot256}=\sqrt{9216}=96\).

4) \(\sqrt{20}\cdot\sqrt{5}-\frac{\sqrt{63}}{\sqrt{7}}=\sqrt{100}-\sqrt{9}=10-3=7\).

Ответ: 1) 18; 2) 4,5; 3) 96; 4) 7.