Вычислите: 1) \frac{3}{8} + \frac{4}{9}; 2) \frac{7}{12} - \frac{3}{8}; 3) 2\frac{5}{8} + 1\frac{3}{10}; 4) 6\frac{7}{10} - 4\frac{5}{12}.

1) \frac{3}{8} + \frac{4}{9} = \frac{3 \cdot 9}{8 \cdot 9} + \frac{4 \cdot 8}{9 \cdot 8} = \frac{27}{72} + \frac{32}{72} = \frac{59}{72}. 2) \frac{7}{12} - \frac{3}{8} = \frac{7 \cdot 2}{12 \cdot 2} - \frac{3 \cdot 3}{8 \cdot 3} = \frac{14}{24} - \frac{9}{24} = \frac{5}{24}. 3) 2\frac{5}{8} + 1\frac{3}{10} = 2 + \frac{5}{8} + 1 + \frac{3}{10} = 3 + \frac{5}{8} + \frac{3}{10} = 3 + \frac{5 \cdot 5}{8 \cdot 5} + \frac{3 \cdot 4}{10 \cdot 4} = 3 + \frac{25}{40} + \frac{12}{40} = 3 + \frac{37}{40} = 3\frac{37}{40}. 4) 6\frac{7}{10} - 4\frac{5}{12} = 6 + \frac{7}{10} - (4 + \frac{5}{12}) = 6 + \frac{7}{10} - 4 - \frac{5}{12} = 2 + \frac{7}{10} - \frac{5}{12} = 2 + \frac{7 \cdot 6}{10 \cdot 6} - \frac{5 \cdot 5}{12 \cdot 5} = 2 + \frac{42}{60} - \frac{25}{60} = 2 + \frac{17}{60} = 2\frac{17}{60}.