57. \(\frac{3}{5}:\left(-\frac{9}{25}\right)\)

\[\frac{3}{5}:\left(-\frac{9}{25}\right)=\frac{3}{5}\cdot\left(-\frac{25}{9}\right)=-\frac{5}{3}=-1\frac{2}{3}.\]

Ответ: \(-1\frac{2}{3}\).