№4 а) $$\frac{x}{-2,3} = \frac{-5,8}{-4,6}$$; в) $$\frac{-\frac{2}{9}}{x} = \frac{11\frac{2}{3}}{-1\frac{2}{5}}$$; б) $$\frac{-2,8}{35} = \frac{-4,2}{x}$$; г) $$\frac{2}{-\frac{7}{3}} = \frac{x}{\frac{5}{6}}$$.

а) $$\frac{x}{-2,3} = \frac{-5,8}{-4,6}$$;

$$\frac{x}{-2,3} = \frac{5,8}{4,6}$$;

$$x = \frac{5,8 \cdot (-2,3)}{4,6}$$;

$$x = \frac{5,8 \cdot (-2,3)}{4,6} = \frac{2,9 \cdot (-2,3)}{2,3} = -2,9$$

б) $$\frac{-2,8}{35} = \frac{-4,2}{x}$$;

$$\frac{-2,8}{35} = \frac{-4,2}{x}$$;

$$x = \frac{-4,2 \cdot 35}{-2,8}$$;

$$x = \frac{-4,2 \cdot 35}{-2,8} = \frac{4,2 \cdot 35}{2,8} = \frac{42 \cdot 35}{28} = \frac{6 \cdot 35}{4} = \frac{3 \cdot 35}{2} = \frac{105}{2} = 52,5$$

в) $$\frac{-\frac{2}{9}}{x} = \frac{11\frac{2}{3}}{-1\frac{2}{5}}$$;

$$\frac{-\frac{2}{9}}{x} = \frac{\frac{35}{3}}{-\frac{7}{5}}$$;

$$x = \frac{-\frac{2}{9}}{ \frac{\frac{35}{3}}{-\frac{7}{5}}} = \frac{-\frac{2}{9}}{-\frac{35}{3} \cdot \frac{5}{7}} = \frac{-\frac{2}{9}}{-\frac{5}{3} \cdot 5} = \frac{-\frac{2}{9}}{-\frac{25}{3}} = -\frac{2}{9} \cdot (-\frac{3}{25}) = \frac{2}{3} \cdot \frac{1}{25} = \frac{2}{75}$$

г) $$\frac{2}{-\frac{7}{3}} = \frac{x}{\frac{5}{6}}$$.

$$\frac{2}{-\frac{7}{3}} = \frac{x}{\frac{5}{6}}$$;

$$x = \frac{2 \cdot \frac{5}{6}}{-\frac{7}{3}} = \frac{\frac{5}{3}}{-\frac{7}{3}} = \frac{5}{3} \cdot (-\frac{3}{7}) = -\frac{5}{7}$$

Ответ: а) -2,9; б) 52,5; в) $$\frac{2}{75}$$; г) -$$\frac{5}{7}$$