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

a) \(\frac{3}{4} - \frac{1}{6} + \frac{11}{12} + \frac{9}{10}\). Приведем к общему знаменателю 60: \(\frac{45 - 10 + 55 + 54}{60} = \frac{144}{60} = \frac{12 * 12}{12 * 5} = \frac{12}{5} = 2\frac{2}{5}\) в) \(\frac{3}{7} \cdot \frac{7}{9} = \frac{3 * 7}{7 * 9} = \frac{3}{9} = \frac{1}{3}\) г) \(\frac{2}{3} : \frac{2}{7} = \frac{2}{3} \cdot \frac{7}{2} = \frac{2 * 7}{3 * 2} = \frac{7}{3} = 2\frac{1}{3}\) д) \(6\frac{5}{6} + 2\frac{3}{8} = 6 + 2 + \frac{5}{6} + \frac{3}{8} = 8 + \frac{20 + 9}{24} = 8 + \frac{29}{24} = 8 + 1\frac{5}{24} = 9\frac{5}{24}\) е) \(3\frac{4}{7} - 2\frac{3}{5} = 3 - 2 + \frac{4}{7} - \frac{3}{5} = 1 + \frac{20 - 21}{35} = 1 - \frac{1}{35} = \frac{34}{35}\) ж) \(2\frac{1}{7} \cdot 3\frac{1}{9} = \frac{15}{7} \cdot \frac{28}{9} = \frac{15 * 28}{7 * 9} = \frac{15 * 4}{9} = \frac{5 * 4}{3} = \frac{20}{3} = 6\frac{2}{3}\) з) \(3\frac{3}{5} : 2\frac{7}{10} = \frac{18}{5} : \frac{27}{10} = \frac{18}{5} \cdot \frac{10}{27} = \frac{18 * 10}{5 * 27} = \frac{2 * 2}{3} = \frac{4}{3} = 1\frac{1}{3}\)