\[\frac{0,9}{1 + \frac{1}{8}} = \frac{0,9}{1\frac{1}{8}} = \frac{9}{10}\ :\frac{9}{8} =\]
\[= \frac{9}{10} \cdot \frac{8}{9} = \frac{4}{5} = 0,8.\]