Tìm x biết: $\frac{3}{7} - \frac{4}{7}:\left( {x - 1} \right) = \frac{5}{7}$.

$\frac{3}{7} - \frac{4}{7}:\left( {x - 1} \right) = \frac{5}{7}$

⇔ $\frac{4}{7}:\left( {x - 1} \right) = \frac{3}{7} - \frac{5}{7} = \frac{{ - 2}}{7}$

⇔ $x - 1 = \frac{4}{7}:\frac{{ - 2}}{7}$

⇔ x – 1 = –2

⇔ x = – 2 + 1

⇔ x = –1

Vậy x = –1.