\[\frac{1}{2}\sqrt{20} < \frac{5}{6}\sqrt{45}\]
\[\frac{1}{2}\sqrt{20} = \frac{1}{2}\sqrt{4 \cdot 5} = \frac{1}{2} \cdot 2\sqrt{5} = \sqrt{5}\]
\[\frac{5}{6}\sqrt{45} = \frac{5}{6}\sqrt{9 \cdot 5} = \frac{5}{6} \cdot 3\sqrt{5} = 2,5\sqrt{5}\]
\[\sqrt{5} < 2,5\sqrt{5}\]