Ответ:

а) \(\frac{9}{13}\cdot\frac{26}{27}=\frac{9\cdot2}{27}=\frac{2}{3}\).

б) \(-\frac{5}{14}\cdot\frac{42}{75}=-\frac{5\cdot3}{75}=-\frac{1}{5}\).

в) \(\frac{17}{24}\cdot\left(-\frac{48}{51}\right)=-\frac{17\cdot2}{51}=-\frac{2}{3}\).

Ответ: а) \(\frac{2}{3}\); б) \(-\frac{1}{5}\); в) \(-\frac{2}{3}\).