4. Сократите дробь: 20/45 = ; 12/72 = ; 136/170 = ; 21/108 = ; 24/36 =

1. \(\frac{20}{45}=\frac{20\mathbin{:}5}{45\mathbin{:}5}=\frac{4}{9}\).
2. \(\frac{12}{72}=\frac{12\mathbin{:}12}{72\mathbin{:}12}=\frac{1}{6}\).
3. \(\frac{136}{170}=\frac{136\mathbin{:}34}{170\mathbin{:}34}=\frac{4}{5}\).
4. \(\frac{21}{108}=\frac{21\mathbin{:}3}{108\mathbin{:}3}=\frac{7}{36}\).
5. \(\frac{24}{36}=\frac{24\mathbin{:}12}{36\mathbin{:}12}=\frac{2}{3}\).

Ответ: \(\frac{4}{9};\ \frac{1}{6};\ \frac{4}{5};\ \frac{7}{36};\ \frac{2}{3}\).