\[2 \frac{5}{8} \cdot (\frac{5}{7} - \frac{3}{5}) - 9 : 2 \frac{1}{4} = \frac{21}{8} \cdot (\frac{25}{35} - \frac{21}{35}) - 9 : \frac{9}{4}\]
\[ = \frac{21}{8} \cdot \frac{4}{35} - 9 \cdot \frac{4}{9}\]
\[= \frac{21 \cdot 4}{8 \cdot 35} - \frac{9 \cdot 4}{9}\]
\[= \frac{84}{280} - 4\]
\[= \frac{3}{10} - 4\]
\[= \frac{3}{10} - \frac{40}{10}\]
\[= -\frac{37}{10}\]
\[= -3.7\]
Ответ: -3.7