19) -1/6 + 5/12

$$
-\frac{1}{6} + \frac{5}{12} = -\frac{1 \cdot 2}{6 \cdot 2} + \frac{5}{12} = -\frac{2}{12} + \frac{5}{12} = \frac{3}{12} = \frac{1}{4}
$$

Ответ: 1/4