Ответ:

  1. \(-1\frac{3}{8}-2\frac{5}{12}=-\frac{11}{8}-\frac{29}{12}=-\frac{33}{24}-\frac{58}{24}=-\frac{91}{24}\).
    \(5\frac{5}{12}=\frac{65}{12}\).
    \(-\frac{91}{24}:\frac{65}{12}=-\frac{91}{24}\cdot\frac{12}{65}=-\frac{7}{10}\).
  2. \(5\frac{8}{9}=\frac{53}{9}\), \(1\frac{17}{36}=\frac{53}{36}\).
    \(\frac{53}{9}:\frac{53}{36}=4\).
    \(4+1\frac{1}{4}=4+\frac{5}{4}=\frac{21}{4}\).
    \(\frac{21}{4}\cdot\frac{5}{21}=\frac{5}{4}\).
  3. \(0,64+0,9=1,54\).
    \(65,7-69,2=-3,5\).
    \(1,54\cdot(-3,5)=-5,39\).

Ответ: 1) \(-\frac{7}{10}\); 2) \(\frac{5}{4}\); 3) \(-5,39\).