Tìm x A. 2/9 + x = 1 B. x + 1/2 = 4/5

* Hướng dẫn giải

$\begin{array}{l}A.\frac{2}{9}+x=1\\ x=1-\frac{2}{9}\\ x=\frac{9}{9}-\frac{2}{9}=\frac{7}{9}\end{array}$                         

$\begin{array}{l}B.x+\frac{1}{2}=\frac{4}{5}\\ x=\frac{4}{5}-\frac{1}{2}\\ x=\frac{8}{10}-\frac{5}{10}\\ x=\frac{3}{10}\end{array}$