5.53 Найдите неизвестный член пропорции: б)

$$\frac{-7\frac{1}{4}}{c} = \frac{4\frac{1}{7}}{1\frac{3}{7}}$$
$$\frac{-\frac{29}{4}}{c} = \frac{\frac{29}{7}}{\frac{10}{7}}$$
$$c = \frac{-\frac{29}{4} \cdot \frac{10}{7}}{\frac{29}{7}} = -\frac{29}{4} \cdot \frac{10}{7} \cdot \frac{7}{29} = -\frac{10}{4} = -2,5$$.