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

Решение:

1. \( 5\frac{5}{28} - 5\frac{1}{3} = \frac{5 \cdot 28 + 5}{28} - \frac{5 \cdot 3 + 1}{3} = \frac{145}{28} - \frac{16}{3} = \frac{145 \cdot 3 - 16 \cdot 28}{84} = \frac{435 - 448}{84} = -\frac{13}{84} \)
2. \( -\frac{13}{84} : 1,25 = -\frac{13}{84} : \frac{5}{4} = -\frac{13}{84} \cdot \frac{4}{5} = -\frac{13}{21 \cdot 5} = -\frac{13}{105} \)
3. \( 1\frac{16}{21} : (-1,5) = \frac{37}{21} : \left( -\frac{3}{2} \right) = \frac{37}{21} \cdot \left( -\frac{2}{3} \right) = -\frac{74}{63} \)
4. \( -\frac{13}{105} - \left( -\frac{74}{63} \right) = -\frac{13}{105} + \frac{74}{63} = \frac{-13 \cdot 3 + 74 \cdot 5}{315} = \frac{-39 + 370}{315} = \frac{331}{315} \)

Ответ: \( \frac{331}{315} \).