a/ \(-x-\dfrac{2}{3}=-\dfrac{6}{7}\)
\(\Leftrightarrow-x=-\dfrac{6}{7}+\dfrac{2}{3}\)
\(\Leftrightarrow-x=-\dfrac{18}{21}+\dfrac{14}{21}\)
\(\Leftrightarrow-x=-\dfrac{4}{21}\)
\(\Leftrightarrow x=\dfrac{4}{21}\)
Vậy ....
b/ \(\left(5x-1\right)\left(2x-\dfrac{1}{3}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}5x-1=0\\2x-\dfrac{1}{3}=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}5x=1\\2x=\dfrac{1}{3}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{5}\\x=\dfrac{1}{6}\end{matrix}\right.\)
Vậy ..