Выполните действия с обыкновенными дробями: сложение и вычитание

**Ответы:** 1) $$\frac{2}{5} + \frac{3}{10} = \frac{4}{10} + \frac{3}{10} = \frac{7}{10}$$ 2) $$\frac{5}{6} - \frac{7}{12} = \frac{10}{12} - \frac{7}{12} = \frac{3}{12} = \frac{1}{4}$$ 3) $$\frac{3}{4} + \frac{1}{8} = \frac{6}{8} + \frac{1}{8} = \frac{7}{8}$$ 4) $$\frac{1}{2} - \frac{1}{3} = \frac{3}{6} - \frac{2}{6} = \frac{1}{6}$$ 5) $$\frac{1}{2} + \frac{2}{7} = \frac{7}{14} + \frac{4}{14} = \frac{11}{14}$$ 6) $$\frac{7}{6} - 1 = \frac{7}{6} - \frac{6}{6} = \frac{1}{6}$$ 7) $$\frac{1}{2} + \frac{1}{4} = \frac{2}{4} + \frac{1}{4} = \frac{3}{4}$$ 8) $$\frac{1}{5} - \frac{1}{6} = \frac{6}{30} - \frac{5}{30} = \frac{1}{30}$$ 9) $$\frac{2}{3} - \frac{2}{5} = \frac{10}{15} - \frac{6}{15} = \frac{4}{15}$$ 10) $$\frac{1}{3} + \frac{1}{4} = \frac{4}{12} + \frac{3}{12} = \frac{7}{12}$$ 11) $$\frac{2}{5} + \frac{4}{15} = \frac{6}{15} + \frac{4}{15} = \frac{10}{15} = \frac{2}{3}$$ 12) $$\frac{1}{4} + \frac{1}{5} = \frac{5}{20} + \frac{4}{20} = \frac{9}{20}$$ 13) $$\frac{7}{9} - \frac{2}{3} = \frac{7}{9} - \frac{6}{9} = \frac{1}{9}$$ 14) $$\frac{3}{20} + \frac{3}{4} = \frac{3}{20} + \frac{15}{20} = \frac{18}{20} = \frac{9}{10}$$ 15) $$\frac{1}{3} - \frac{1}{6} = \frac{2}{6} - \frac{1}{6} = \frac{1}{6}$$ 16) $$\frac{1}{1} - \frac{1}{3} = 1 - \frac{1}{3} = \frac{2}{3}$$