Решение:
а) $\frac{-1}{2} + \frac{-1}{4} = \frac{-2}{4} + \frac{-1}{4} = \frac{-2 - 1}{4} = \frac{-3}{4} = -\frac{3}{4};$
б) $\frac{-1}{3} + \frac{1}{6} = \frac{-2}{6} + \frac{1}{6} = \frac{-2 + 1}{6} = \frac{-1}{6} = -\frac{1}{6};$
в) $-\frac{1}{2} + \frac{1}{6} = \frac{-3}{6} + \frac{1}{6} = \frac{-3 + 1}{6} = \frac{-2}{6} = -\frac{1}{3};$
г) $\frac{1}{8} + \frac{-1}{4} = \frac{1}{8} + \frac{-2}{8} = \frac{1 - 2}{8} = \frac{-1}{8} = -\frac{1}{8};$
д) $\frac{3}{10} + \frac{-7}{100} = \frac{30}{100} + \frac{-7}{100} = \frac{30 - 7}{100} = \frac{23}{100}.$
Ответ:
а) $-\frac{3}{4};$
б) $-\frac{1}{6};$
в) $-\frac{1}{3};$
г) $-\frac{1}{8};$
д) $\frac{23}{100}.$