2. Найдите значение выражения: a) \frac{2}{3} + \frac{1}{6} б) -\frac{1}{3} + \frac{2}{5} в) -\frac{7}{9} + \frac{1}{6}

а) \(\frac{2}{3} + \frac{1}{6} = \frac{2 \cdot 2}{3 \cdot 2} + \frac{1}{6} = \frac{4}{6} + \frac{1}{6} = \frac{4 + 1}{6} = \frac{5}{6}\)

б) \(-\frac{1}{3} + \frac{2}{5} = -\frac{1 \cdot 5}{3 \cdot 5} + \frac{2 \cdot 3}{5 \cdot 3} = -\frac{5}{15} + \frac{6}{15} = \frac{-5 + 6}{15} = \frac{1}{15}\)

в) \(-\frac{7}{9} + \frac{1}{6} = -\frac{7 \cdot 2}{9 \cdot 2} + \frac{1 \cdot 3}{6 \cdot 3} = -\frac{14}{18} + \frac{3}{18} = \frac{-14 + 3}{18} = -\frac{11}{18}\)