Привет! Разберёмся с примерами, где один знаменатель делится на другой без остатка.
\[\frac{1}{10} + \frac{2}{5} = \frac{1}{10} + \frac{2 \cdot 2}{5 \cdot 2} = \frac{1}{10} + \frac{4}{10} = \frac{5}{10} = \frac{1}{2}\]
\[\frac{1}{3} - \frac{1}{9} = \frac{1 \cdot 3}{3 \cdot 3} - \frac{1}{9} = \frac{3}{9} - \frac{1}{9} = \frac{2}{9}\]
\[\frac{5}{12} + \frac{5}{6} = \frac{5}{12} + \frac{5 \cdot 2}{6 \cdot 2} = \frac{5}{12} + \frac{10}{12} = \frac{15}{12} = \frac{5}{4} = 1\frac{1}{4}\]
\[\frac{4}{7} - \frac{2}{14} = \frac{4 \cdot 2}{7 \cdot 2} - \frac{2}{14} = \frac{8}{14} - \frac{2}{14} = \frac{6}{14} = \frac{3}{7}\]
\[\frac{1}{30} + \frac{4}{5} = \frac{1}{30} + \frac{4 \cdot 6}{5 \cdot 6} = \frac{1}{30} + \frac{24}{30} = \frac{25}{30} = \frac{5}{6}\]