Решение:
\[ \frac{7}{13} - \frac{9}{13} = \frac{7 - 9}{13} = \frac{-2}{13} \]
\[ \frac{5}{9} \times \frac{-2}{13} = \frac{5 \times (-2)}{9 \times 13} = \frac{-10}{117} \]
Ответ: -10/117