$\dfrac{3}{7}$ $x-1=$$\dfrac{1}{7}$ $x(3x−7)$
$\dfrac{3x}{7}$ $-1=$$\dfrac{1}{7}$ $x(3x−7)$
$\dfrac{3x}{7}$ $- 1=$$\dfrac{x(3x−7)}{7}$
$⇔3x−7=x(3x−7)$
$⇔3x−7=3x^2−7x$
$⇔10x−7−3x^2=0$
$⇔3x^2−3x−7x+7=0$
$⇔3x(x−1)−7(x−1)=0$
$⇔(x−1)(3x−7)=0$
TH1:$⇔x-1=0$ ⇔ TH2:$⇔3x−7=0$
$⇔x=1$ ⇔ $⇔x=$$\dfrac{7}{3}$
$⇒x=1;$$\dfrac{7}{3}$