Решение:
а) $х * \frac{3}{5} = -\frac{4}{15}$
$х = -\frac{4}{15} : \frac{3}{5} = -\frac{4}{15} * \frac{5}{3} = -\frac{4 * \overset{1}{\cancel{5}}}{\underset{3}{\cancel{15}} * 3} = -\frac{4 * 1}{3 * 3} = -\frac{4}{9}$;
б) $-\frac{2}{3} * х = \frac{4}{7}$
$х = \frac{4}{7} : (-\frac{2}{3}) = \frac{4}{7} * (-\frac{3}{2}) = -\frac{\overset{2}{\cancel{4}} * 3}{7 * \underset{1}{\cancel{2}}} = -\frac{2 * 3}{7 * 1} = -\frac{6}{7}$;
в) $х : \frac{1}{2} = -\frac{1}{4}$
$х = -\frac{1}{4} * \frac{1}{2} = -\frac{1 * 1}{4 * 2} = -\frac{1}{8}$;
г) $\frac{2}{7} : х = -\frac{22}{21}$
$х = \frac{2}{7} : (-\frac{22}{21}) = \frac{2}{7} * (-\frac{21}{22}) = -\frac{\overset{1}{\cancel{2}} * \overset{3}{\cancel{21}}}{\underset{1}{\cancel{7}} * \underset{11}{\cancel{22}}} = -\frac{1 * 3}{1 * 11} = -\frac{3}{11}$.
Ответ:
а) $-\frac{4}{9}$;
б) $-\frac{6}{7}$;
в) $-\frac{1}{8}$;
г) $-\frac{3}{11}$.