18. Вычислите: \(\left(\frac{8}{11}-\frac{20}{55}\right)\cdot\frac{66}{20}\).

\(\frac{20}{55}=\frac{4}{11}\), поэтому:

\(\left(\frac{8}{11}-\frac{4}{11}\right)\cdot\frac{66}{20}=\frac{4}{11}\cdot\frac{66}{20}=\frac{24}{20}=\frac{6}{5}\).

Ответ: \(\frac{6}{5}\).