Hướng dẫn giải
Đáp án đúng là: B
\(\left( {\frac{2}{3} - \frac{5}{9}} \right)x + \frac{3}{4} = \frac{1}{6}\)
\(\left( {\frac{6}{9} - \frac{5}{9}} \right)x = \frac{1}{6} - \frac{3}{4}\)
\(\frac{1}{9}x = \frac{2}{{12}} - \frac{9}{{12}}\)
\(\frac{1}{9}x = \frac{{ - 7}}{{12}}\)
\(x = \frac{{ - 7}}{{12}}:\frac{1}{9}\)
\(x = \frac{{ - 7}}{{12}} \cdot 9\)
\(x = \frac{{ - 21}}{4}\)
Vậy \(x = \frac{{ - 21}}{4}\)