Tìm x theo cách lớp 5 ạ: a) X/12 -1/4 = 2/3÷2 b) 2/5 + x/9 = 2 – 1 $\frac{1}{2}$

a, $\frac{x}{12}-\frac{1}{4}= \frac{2}{3}:2$

    $\frac{x}{12}= \frac{1}{4}+\frac{2}{3}:2$  

    $\frac{x}{12}= \frac{1}{4}+\frac{1}{3}$

    $\frac{x}{12}= \frac{7}{12}$

    $x= 7$

b, $\frac{2}{5}+\frac{x}{9}= 2-1\frac{1}{2}$

    $\frac{2}{5}+\frac{x}{9}= \frac{1}{2}$

    $\frac{x}{9}= \frac{1}{2}-\frac{2}{5}$

    $\frac{x}{9}= \frac{1}{10}$

    $x= \frac{1}{10}×9= \frac{9}{10}$