18 (3-2):3+

Решим пример:

$$\begin{aligned}
\left(3\frac{13}{20} - 2\frac{3}{4}\right) : 3 + \frac{3}{4} = \left(\frac{73}{20} - \frac{11}{4}\right) \cdot \frac{1}{3} + \frac{3}{4} = \left(\frac{73 - 55}{20}\right) \cdot \frac{1}{3} + \frac{3}{4} = \frac{18}{20} \cdot \frac{1}{3} + \frac{3}{4} = \frac{3}{10} + \frac{3}{4} = \frac{6 + 15}{20} = \frac{21}{20} = 1\frac{1}{20}
\end{aligned}$$

Ответ: $$1\frac{1}{20}$$