2. Выполните действия: \(\frac{20!}{18!}\); \(\frac{23!}{21!}\); \(\frac{91!}{61!}\); \(0.2^3\).

1. \(\frac{20!}{18!}=\frac{20\cdot19\cdot18!}{18!}=20\cdot19=380\).
2. \(\frac{23!}{21!}=\frac{23\cdot22\cdot21!}{21!}=23\cdot22=506\).
3. \(\frac{91!}{61!}=62\cdot63\cdot64\cdot\ldots\cdot91\).
4. \(0.2^3=0.2\cdot0.2\cdot0.2=0.008\).

Ответ: 380; 506; \(62\cdot63\cdot\ldots\cdot91\); 0.008.