Сократите дроби: 20/25; 36/72; 105/30.

1. \(\frac{20}{25}=\frac{20:5}{25:5}=\frac{4}{5}\).
2. \(\frac{36}{72}=\frac{36:36}{72:36}=\frac{1}{2}\).
3. \(\frac{105}{30}=\frac{105:15}{30:15}=\frac{7}{2}\).

Ответ: \(\frac{4}{5};\ \frac{1}{2};\ \frac{7}{2}\).