Ответ:

  1. \( -\frac{7}{18}+\frac{11}{12}=-\frac{14}{36}+\frac{33}{36}=\frac{19}{36} \).
    \(\frac{19}{36}:\left(-\frac{19}{48}\right)=\frac{19}{36}\cdot\left(-\frac{48}{19}\right)=-\frac{4}{3}\).
  2. \(6\frac{3}{4}-5\frac{1}{8}=\frac{27}{4}-\frac{41}{8}=\frac{54-41}{8}=\frac{13}{8}\).
    \(1\frac{9}{32}=\frac{41}{32}\).
    \(\frac{13}{8}:\frac{41}{32}\cdot\frac{5}{11}=\frac{13}{8}\cdot\frac{32}{41}\cdot\frac{5}{11}=\frac{260}{451}\).
  3. \(17,6:55=\frac{176}{10}:55=\frac{8}{25}\).
    \(1-\frac{8}{25}=\frac{17}{25}\).
    \(-\frac{2}{17}\cdot\frac{17}{25}=-\frac{2}{25}\).

Ответ: 1) \(-\frac{4}{3}\); 2) \(\frac{260}{451}\); 3) \(-\frac{2}{25}\).