Решение:
а) $\frac{(-1) * 3}{6 * (-4)} = \frac{(-1) * \overset{1}{\cancel{(3)}}}{\underset{2}{\cancel{6}} * (-4)} = \frac{(-1) * 1}{2 * (-4)} = \frac{-1}{-8} = \frac{1}{8};$
б) $\frac{(-3) * 4}{6 * (-5)} = \frac{\overset{-1}{\cancel{(-3)}} * 4}{\underset{2}{\cancel{6}} * (-5)} = \frac{(-1) * \overset{2}{\cancel{4}}}{\underset{1}{\cancel{2}} * (-5)} = \frac{(-1) * 2}{1 * (-5)} = \frac{-2}{-5} = \frac{2}{5};$
в) $\frac{(-4) * 10}{(-30) * 14} = \frac{\overset{-2}{\cancel{(-4)}} * \overset{1}{\cancel{10}}}{\underset{-3}{\cancel{(-30)}} * \underset{7}{\cancel{14}}} = \frac{(-2) * 1}{(-3) * 7} = \frac{-2}{-21} = \frac{2}{21};$
г) $\frac{(-8) * 18}{(-28) * 6} = \frac{\overset{2}{\cancel{(-8)}} * \overset{3}{\cancel{18}}}{\underset{7}{\cancel{(-28)}} * \underset{1}{\cancel{6}}} = \frac{2 * 3}{7 * 1} = \frac{6}{7};$
д) $\frac{(-12) * (-5)}{(-21) * 10} = \frac{\overset{4}{\cancel{(-12)}} * \overset{-1}{\cancel{(-5)}}}{\underset{7}{\cancel{(-21)}} * \underset{2}{\cancel{10}}} = \frac{\overset{2}{\cancel{4}} * (-1)}{7 * \underset{1}{\cancel{2}}} = \frac{2 * (-1)}{7 * 1} = -\frac{2}{7};$
е) $\frac{(-75) * (-24)}{(-32) * (-100)} = \frac{\overset{3}{\cancel{(-75)}} * \overset{3}{\cancel{(-24)}}}{\underset{4}{\cancel{(-32)}} * \underset{4}{\cancel{(-100)}}} = \frac{3 * 3}{4 * 4} = \frac{9}{16}.$
Ответ:
а) $\frac{1}{8};$
б) $\frac{2}{5};$
в) $\frac{2}{21};$
г) $\frac{6}{7};$
д) $-\frac{2}{7};$
е) $\frac{9}{16}.$