tìm x, biết: a) x -4/5 = -3/10 ;

* Hướng dẫn giải

$\begin{array}{l}\mathrm{a}) \mathrm{x}-\frac{4}{5}=\frac{-3}{10}\\ \mathrm{x}=\frac{-3}{10}+\frac{4}{5}\\ \mathrm{x}=\frac{-3}{10}+\frac{4.2}{5.2}\\ \mathrm{x}=\frac{-3}{10}+\frac{8}{10}\\ \mathrm{x}=\frac{5}{10}\\ \mathrm{x}=\frac{1}{2}\\ \mathrm{Vậy} \mathrm{x}=\frac{1}{2}\end{array}$