4) 2 1/10 · 4 1/6 + 5 · 3/8 − 9/20 · 6

\(2\frac{1}{10}\cdot4\frac{1}{6}=\frac{21}{10}\cdot\frac{25}{6}=\frac{35}{4}\).

\(5\cdot\frac{3}{8}=\frac{15}{8}\), а \(\frac{9}{20}\cdot6=\frac{27}{10}\).

\(\frac{35}{4}+\frac{15}{8}-\frac{27}{10}=\frac{350+75-108}{40}=\frac{317}{40}=7\frac{37}{40}\).

Ответ: \(7\frac{37}{40}\).