Ответ:

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

\(-15,3-24\frac{5}{9}=-\frac{153}{10}-\frac{221}{9}=-\frac{1377+2210}{90}=-\frac{3587}{90}\).

\(\frac{5}{6}\cdot\left(-\frac{3587}{90}\right)=-\frac{17935}{540}=-\frac{3587}{108}\).

Ответ: \(-\frac{3587}{108}\).