\[\frac{9}{10}\ и\ \frac{4}{5}\]
\[\frac{4}{5} = \frac{4 \cdot 2}{10} = \frac{8}{10};\]
\[\frac{9}{10} > \frac{8}{10}.\]
\[\frac{9}{10} > \frac{4}{5}.\]