\[\boxed{\text{5.357.}}\]
\[\textbf{а)}\ \frac{6}{10} = \frac{3}{5};\ \ \ \ \ \ \ \ \frac{6}{18} = \frac{1}{3};\ \ \ \ \ \ \ \]
\[\text{\ \ }\frac{9}{15} = \frac{3}{5};\ \ \ \ \ \ \ \frac{9}{24} = \frac{3}{8}\text{.\ }\]
\[\textbf{б)}\ \frac{2}{12} = \frac{1}{6};\ \ \ \ \ \ \ \ \frac{3}{15} = \frac{1}{5};\ \ \ \ \ \ \]
\[\text{\ \ \ }\frac{30}{6} = \frac{5}{1};\ \ \ \ \ \ \ \ \ \ \frac{7}{42} = \frac{1}{6}\text{.\ }\]
\[\textbf{в)}\ \frac{12}{60} = \frac{1}{5};\ \ \ \ \ \ \ \ \ \frac{99}{22} = \frac{9}{2};\ \ \ \ \ \ \]
\[\text{\ \ }\frac{5}{100} = \frac{1}{20};\ \ \ \ \ \ \frac{20}{1\ 000} = \frac{1}{50}\text{.\ \ }\]