C

- Hướng dẫn giải

\(\begin{array}{l}
\frac{1}{2} + \left( {\frac{{ - 4}}{3}} \right)x = \frac{5}{6}\\
 \Leftrightarrow \left( {\frac{{ - 4}}{3}} \right)x = \frac{5}{6} - \frac{1}{2}\\
 \Leftrightarrow \left( {\frac{{ - 4}}{3}} \right)x = \frac{1}{3}\\
 \Leftrightarrow x = \frac{1}{3}:\left( {\frac{{ - 4}}{3}} \right)\\
 \Leftrightarrow x =  - \frac{1}{4}
\end{array}\)