a) 2,8 = 4 ; x-2 x 6 6) 3x:=1:3.

Решим уравнения:

a) $$ \frac{2.8}{x-2} = \frac{4}{x} $$

$$ 2.8x = 4(x-2) $$

$$ 2.8x = 4x - 8 $$

$$ 4x - 2.8x = 8 $$

$$ 1.2x = 8 $$

$$ x = \frac{8}{1.2} $$

$$ x = \frac{80}{12} $$

$$ x = \frac{20}{3} $$

$$ x = 6\frac{2}{3} $$

б) $$ 3x : \frac{6}{7} = 1\frac{1}{6} : 3\frac{1}{3} $$

$$ 3x : \frac{6}{7} = \frac{7}{6} : \frac{10}{3} $$

$$ 3x : \frac{6}{7} = \frac{7}{6} \cdot \frac{3}{10} $$

$$ 3x : \frac{6}{7} = \frac{7}{2} \cdot \frac{1}{10} $$

$$ 3x : \frac{6}{7} = \frac{7}{20} $$

$$ 3x = \frac{7}{20} \cdot \frac{6}{7} $$

$$ 3x = \frac{3}{10} $$

$$ x = \frac{3}{10} : 3 $$

$$ x = \frac{3}{10} \cdot \frac{1}{3} $$

$$ x = \frac{1}{10} $$

Ответ: a) $$x=6\frac{2}{3}$$, б) $$x=\frac{1}{10}$$