\[ \left( \frac{6}{7}x - \frac{1}{2} \right) \cdot 14 = \frac{6}{7}x \cdot 14 - \frac{1}{2} \cdot 14 = 3 \]
\[ \frac{6 \cdot 14}{7}x - \frac{14}{2} = 3 \]
\[ 6 \cdot 2 x - 7 = 3 \]
\[ 12x - 7 = 3 \]
\[ 12x = 3 + 7 \]
\[ 12x = 10 \]
\[ x = \frac{10}{12} \]
\[ x = \frac{5}{6} \]
Ответ: \( x = \frac{5}{6} \).