Tìm x, biết: a) -7/9x = 3 1/2

* Hướng dẫn giải

$$\begin{gathered} a) \frac{-7}{9}\mathrm{x}=3\frac{1}{2} \\ \frac{-7}{9}\mathrm{x}=\frac{2.3+1}{2} \\ \frac{-7}{9}\mathrm{x}=\frac{7}{2} \\ \mathrm{x}=\frac{7}{2}:\left(\frac{-7}{9}\right) \\ \mathrm{x}=\frac{7}{2}.\left(\frac{-9}{7}\right) \\ \mathrm{Vậy} \mathrm{x}=\frac{-9}{2} \end{gathered}$$