( x + $\frac{1}{4}$ ) x $\frac{12}{9}$ = $\frac{2}{3}$
⇔ x + $\frac{1}{4}$ = $\frac{2}{3}$ : $\frac{12}{9}$
⇔ x + $\frac{1}{4}$ = $\frac{2}{3}$ x $\frac{9}{12}$
⇔ x + $\frac{1}{4}$ = $\frac{1}{2}$
⇔ x = $\frac{1}{2}$ - $\frac{1}{4}$
⇔ x = $\frac{2}{4}$ - $\frac{1}{4}$
⇔ x = $\frac{1}{4}$
Xin hay nhất ạ cảm ơn bạn!!!