5. Выполните сложение: a) -1/2 + 1/4 б) 1/9 + (-2/3) в) -3/8 + (-1/2)

a) \(-\frac{1}{2} + \frac{1}{4} = -\frac{2}{4} + \frac{1}{4} = -\frac{1}{4}\) б) \(\frac{1}{9} + \left(-\frac{2}{3}\right) = \frac{1}{9} - \frac{6}{9} = -\frac{5}{9}\) в) \(-\frac{3}{8} + \left(-\frac{1}{2}\right) = -\frac{3}{8} - \frac{4}{8} = -\frac{7}{8}\)