№ 3. Выполните действия: a) \frac{5}{6} - \frac{3}{4} ; б) 4\frac{2}{5} + 3\frac{5}{6}; в) 2\frac{1}{7} \cdot 3\frac{1}{9}; г) 1\frac{1}{8} : \frac{3}{4}.

а) $$\frac{5}{6} - \frac{3}{4} = \frac{5 \times 2}{6 \times 2} - \frac{3 \times 3}{4 \times 3} = \frac{10}{12} - \frac{9}{12} = \frac{1}{12}$$

б) $$4\frac{2}{5} + 3\frac{5}{6} = 4 + \frac{2}{5} + 3 + \frac{5}{6} = 7 + \frac{2 \times 6}{5 \times 6} + \frac{5 \times 5}{6 \times 5} = 7 + \frac{12}{30} + \frac{25}{30} = 7 + \frac{37}{30} = 7 + 1\frac{7}{30} = 8\frac{7}{30}$$

в) $$2\frac{1}{7} \cdot 3\frac{1}{9} = \frac{15}{7} \cdot \frac{28}{9} = \frac{15 \cdot 28}{7 \cdot 9} = \frac{15 \cdot 4}{1 \cdot 9} = \frac{60}{9} = \frac{20}{3} = 6\frac{2}{3}$$

г) $$1\frac{1}{8} : \frac{3}{4} = \frac{9}{8} : \frac{3}{4} = \frac{9}{8} \cdot \frac{4}{3} = \frac{9 \cdot 4}{8 \cdot 3} = \frac{3 \cdot 1}{2 \cdot 1} = \frac{3}{2} = 1\frac{1}{2}$$

Ответ: а) $$\frac{1}{12}$$; б) $$8\frac{7}{30}$$; в) $$6\frac{2}{3}$$; г) $$1\frac{1}{2}$$