Ответ:

\(\frac{5}{18}-\frac{7}{24}=\frac{20-21}{72}=-\frac{1}{72}\).

\(3\frac{3}{5}\cdot\left(-\frac{1}{72}\right)=\frac{18}{5}\cdot\left(-\frac{1}{72}\right)=-\frac{1}{20}\).

\(\frac{3}{4}-\frac{1}{20}-\frac{1}{5}=\frac{15-1-4}{20}=\frac{10}{20}=\frac{1}{2}\).

Ответ: \(\frac{1}{2}\).