Đáp án đúng: B
Giải chi tiết:\(\begin{array}{l}\,\,\frac{1}{2} - \left( {\frac{2}{3}x - \frac{1}{3}} \right) = \frac{2}{3}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{2}{3}x - \frac{1}{3} = \frac{1}{2} - \frac{2}{3}\,\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{2}{3}x - \frac{1}{3} = \frac{{ - 1}}{6}\,\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{2}{3}x\,\,\,\,\,\,\,\,\, = \frac{{ - 1}}{6}\, + \frac{1}{3}\,\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{2}{3}x\,\,\,\,\,\,\,\,\,\, = \frac{1}{6}\,\,\,\,\,\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\, = \frac{1}{6}:\frac{2}{3}\,\,\,\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\,\, = \frac{1}{4}\,\,\,\end{array}\)
Chọn B
