Вычислите: 1) \frac{4}{7} + \frac{2}{5}; 2) \frac{7}{12} - \frac{5}{9}; 3) 2\frac{3}{4} + 3\frac{2}{5}; 4) 3\frac{4}{9} - 2\frac{1}{6}.

1) \frac{4}{7} + \frac{2}{5} = \frac{20}{35} + \frac{14}{35} = \frac{34}{35}. 2) \frac{7}{12} - \frac{5}{9} = \frac{21}{36} - \frac{20}{36} = \frac{1}{36}. 3) 2\frac{3}{4} + 3\frac{2}{5} = \frac{11}{4} + \frac{17}{5} = \frac{55}{20} + \frac{68}{20} = \frac{123}{20} = 6\frac{3}{20}. 4) 3\frac{4}{9} - 2\frac{1}{6} = \frac{31}{9} - \frac{13}{6} = \frac{62}{18} - \frac{39}{18} = \frac{23}{18} = 1\frac{5}{18}.