5. Выполните действия: a) $\frac{3}{6} - \frac{1}{6}$; б) $\frac{11}{12} + \frac{9}{12}$; в) $\frac{3}{7} \cdot \frac{7}{9}$; г) $\frac{2}{3} \cdot \frac{3}{5}$ д) $6\frac{5}{8} + 2\frac{3}{8}$; е) $3\frac{4}{7} - 2\frac{3}{7}$; ж) $2\frac{1}{7} \cdot 3\frac{1}{9}$; з) $3\frac{3}{5} : 2\frac{7}{10}$.

Решение примеров: a) $\frac{3}{6} - \frac{1}{6} = \frac{3-1}{6} = \frac{2}{6} = \frac{1}{3}$ б) $\frac{11}{12} + \frac{9}{12} = \frac{11+9}{12} = \frac{20}{12} = \frac{5}{3} = 1\frac{2}{3}$ в) $\frac{3}{7} \cdot \frac{7}{9} = \frac{3 \cdot 7}{7 \cdot 9} = \frac{21}{63} = \frac{1}{3}$ г) $\frac{2}{3} \cdot \frac{3}{5} = \frac{2 \cdot 3}{3 \cdot 5} = \frac{6}{15} = \frac{2}{5}$ д) $6\frac{5}{8} + 2\frac{3}{8} = (6+2) + (\frac{5}{8} + \frac{3}{8}) = 8 + \frac{8}{8} = 8 + 1 = 9$ е) $3\frac{4}{7} - 2\frac{3}{7} = (3-2) + (\frac{4}{7} - \frac{3}{7}) = 1 + \frac{1}{7} = 1\frac{1}{7}$ ж) $2\frac{1}{7} \cdot 3\frac{1}{9} = \frac{15}{7} \cdot \frac{28}{9} = \frac{15 \cdot 28}{7 \cdot 9} = \frac{15 \cdot 4}{1 \cdot 9} = \frac{60}{9} = \frac{20}{3} = 6\frac{2}{3}$ з) $3\frac{3}{5} : 2\frac{7}{10} = \frac{18}{5} : \frac{27}{10} = \frac{18}{5} \cdot \frac{10}{27} = \frac{18 \cdot 10}{5 \cdot 27} = \frac{2 \cdot 2}{1 \cdot 3} = \frac{4}{3} = 1\frac{1}{3}$