Ответ:

\(15,3=\frac{153}{10}\), \(24\frac{5}{9}=\frac{221}{9}\).

\[\frac{5}{6}\left(-\frac{153}{10}-\frac{221}{9}\right)=\frac{5}{6}\cdot\left(-\frac{3587}{90}\right)=-\frac{3587}{108}.\]

Ответ: \(-\frac{3587}{108}\).