13. Вычислите: $$\frac{5}{4} + 2\frac{1}{3} \cdot (-\frac{5}{21} + \frac{9}{14}) - 1\frac{7}{12}$$.

$$\frac{5}{4} + 2\frac{1}{3} \cdot (-\frac{5}{21} + \frac{9}{14}) - 1\frac{7}{12} = \frac{5}{4} + \frac{7}{3} \cdot (-\frac{10}{42} + \frac{27}{42}) - \frac{19}{12} =$$ $$\frac{5}{4} + \frac{7}{3} \cdot \frac{17}{42} - \frac{19}{12} = \frac{5}{4} + \frac{17}{18} - \frac{19}{12} = \frac{45}{36} + \frac{34}{36} - \frac{57}{36} = \frac{45+34-57}{36} = \frac{22}{36} = \frac{11}{18}$$. **Ответ: $$\frac{11}{18}$$**