\( (-4.3 - 1.2) : \left(-1\frac{7}{15}\right) = (-5.5) : \left(-\frac{15+7}{15}\right) = -5.5 : \left(-\frac{22}{15}\right) = -\frac{55}{10} : \left(-\frac{22}{15}\right) = -\frac{11}{2} : \left(-\frac{22}{15}\right) = \frac{11}{2} \cdot \frac{15}{22} = \frac{1}{2} \cdot \frac{15}{2} = \frac{15}{4} = 3.75 \)
Ответ: 3.75.