\(\frac{4}{9}:8-\left(\frac{1}{4}+\frac{9}{20}\right):1\frac{4}{5}\)
\(=\frac{1}{18}-\frac{7}{10}\cdot\frac{5}{9}=\frac{1}{18}-\frac{7}{18}=-\frac{1}{3}\)
\(\frac{4}{9}:8-\left(\frac{1}{4}+\frac{9}{20}\right):1\frac{4}{5}\)
\(=\frac{1}{18}-\frac{5+9}{20}\times\frac{5}{9}\)
\(=\frac{1}{18}-\frac{14\times5}{20\times9}\)
\(\frac{1}{18}-\frac{14}{36}=\frac{2-14}{36}=\frac{-12}{36}=\frac{-1}{3}\)