Вычислите \(0,1\cdot\sqrt{20}:\\sqrt{45}-2\frac{17}{30}\).

\(\sqrt{20}=2\sqrt5\), \(\sqrt{45}=3\sqrt5\).

\(0,1\cdot\sqrt{20}:[?\sqrt{45}=0,1\cdot\frac{2}{3}=\frac{1}{15}\).

\(2\frac{17}{30}=\frac{77}{30}\).

\(\frac{1}{15}-\frac{77}{30}=\frac{2-77}{30}=-\frac{75}{30}=-2,5\).

Ответ: \(-2,5\).