(+)

$$\left(\frac{1}{3} - \frac{1}{4}\right) : \left(\frac{1}{5} - \frac{5}{6}\right) = \left(\frac{4 - 3}{12}\right) : \left(\frac{6 - 25}{30}\right) = \frac{1}{12} : \frac{-19}{30} = \frac{1}{12} \cdot \frac{-30}{19} = -\frac{30}{12 \cdot 19} = -\frac{5}{2 \cdot 19} = -\frac{5}{38}$$

Ответ: -5/38