г) -1$$\frac{3}{4} : 5\frac{1}{4} = -\frac{7}{4} : \frac{21}{4} = -\frac{7}{4} \cdot \frac{4}{21} = -\frac{7 \cdot 4}{4 \cdot 21} = -\frac{1 \cdot 1}{1 \cdot 3} = -\frac{1}{3}
Ответ: