Ответ:

\(3\frac{11}{27}-2\frac{17}{18}=\frac{92}{27}-\frac{53}{18}=\frac{184}{54}-\frac{159}{54}=\frac{25}{54}\).

\(1\frac{23}{27}=\frac{50}{27}\), поэтому
\(\frac{25}{54}:\frac{50}{27}=\frac{25}{54}\cdot\frac{27}{50}=\frac{1}{4}\).

\(3\frac{3}{5}:3=\frac{18}{5}:3=\frac{6}{5}\).

\(\frac{1}{4}+\frac{6}{5}=\frac{5}{20}+\frac{24}{20}=\frac{29}{20}=1\frac{9}{20}\).

Ответ: \(1\frac{9}{20}\).