3) \(\left(5\frac{5}{28}-5\frac{1}{3}\cdot1,25-1\frac{16}{21}\right):(-1,5)\)

Преобразуем десятичные дроби: \(1,25=\frac54\), \(-1,5=-\frac32\).

\(5\frac{5}{28}=\frac{145}{28}\), \(5\frac13=\frac{16}{3}\), \(1\frac{16}{21}=\frac{37}{21}\).

\(\frac{16}{3}\cdot\frac54=\frac{20}{3}\).

Вычислим скобки:

\[\frac{145}{28}-\frac{20}{3}-\frac{37}{21}=\frac{435-560-148}{84}=-\frac{273}{84}=-\frac{13}{4}.\]

\[ -\frac{13}{4}:\left(-\frac32\right)=-\frac{13}{4}\cdot\left(-\frac23\right)=\frac{13}{6}.\]

Ответ: \(\frac{13}{6}=2\frac16\).