1) √63 · √28; 2) √20 · √5; 3) √50 : √8; 4) √12 : √27.

1. \(\sqrt{63}\cdot\sqrt{28}=\sqrt{63\cdot28}=\sqrt{1764}=42\).
2. \(\sqrt{20}\cdot\sqrt{5}=\sqrt{20\cdot5}=\sqrt{100}=10\).
3. \(\sqrt{50}:\sqrt{8}=\sqrt{\frac{50}{8}}=\sqrt{\frac{25}{4}}=\frac{5}{2}\).
4. \(\sqrt{12}:\sqrt{27}=\sqrt{\frac{12}{27}}=\sqrt{\frac{4}{9}}=\frac{2}{3}\).

Ответ: 1) 42; 2) 10; 3) \(\frac{5}{2}\); 4) \(\frac{2}{3}\).