10 20-19-(3)

Решим пример:

$$\begin{aligned}
20 - 19\frac{1}{2} \cdot \frac{2}{3} : \left(\frac{3}{4} - \frac{3}{5}\right) = 20 - \frac{39}{2} \cdot \frac{2}{3} : \left(\frac{15 - 12}{20}\right) = 20 - \frac{13}{1} \cdot \frac{1}{1} : \frac{3}{20} = 20 - 13 \cdot \frac{20}{3} = 20 - \frac{260}{3} = \frac{60 - 260}{3} = \frac{-200}{3} = -66\frac{2}{3}
\end{aligned}$$

Ответ: $$-66\frac{2}{3}$$