Tìm x: 

- Hướng dẫn giải

$$\begin{gathered} \frac{9}{2}-\left[\frac{2}{3}-\left(x+\frac{7}{4}\right)\right]=\frac{-5}{4} \\ \begin{array}{l}\frac{2}{3}-\left(x+\frac{7}{4}\right)=\frac{9}{2}-\left(\frac{-5}{4}\right)\\ \frac{2}{3}-\left(x+\frac{7}{4}\right)=\frac{9}{2}+\frac{5}{4}\\ \frac{2}{3}-\left(x+\frac{7}{4}\right)=\frac{23}{4}\\ x+\frac{7}{4}=\frac{2}{3}-\frac{23}{4}\\ x+\frac{7}{4}=\frac{8-69}{12}\\ x+\frac{7}{4}=\frac{-57}{12}\\ x+\frac{7}{4}=\frac{-19}{4}\\ x=\frac{-19}{4}-\frac{7}{4}\\ x=\frac{-26}{4}\\ x=\frac{-13}{2}\end{array} \end{gathered}$$