78:1-(3-2)

Решим пример:

$$\begin{aligned}
8\frac{1}{4} : 1\frac{1}{10} - \left(3\frac{2}{5} - 2\frac{4}{7}\right) = \frac{33}{4} : \frac{11}{10} - \left(\frac{17}{5} - \frac{18}{7}\right) = \frac{33}{4} \cdot \frac{10}{11} - \left(\frac{119 - 90}{35}\right) = \frac{3}{2} \cdot \frac{5}{1} - \frac{29}{35} = \frac{15}{2} - \frac{29}{35} = \frac{15 \cdot 35 - 29 \cdot 2}{70} = \frac{525 - 58}{70} = \frac{467}{70} = 6\frac{47}{70}
\end{aligned}$$

Ответ: $$6\frac{47}{70}$$