Đáp án:
a,$\frac{2}{3}$ .x+ $\frac{1}{4}$ =$\frac{7}{12}$
<=> $\frac{2}{3}$.x= $\frac{7}{12}$ -$\frac{1}{4}$
<=> $\frac{2}{3}$.x= $\frac{1}{3}$
<=>x=$\frac{1}{3}$: $\frac{2}{3}$
<=>x=$\frac{3}{6}$= $\frac{1}{2}$
b, $\frac{2}{3}$+ $\frac{1}{3}$ :x=$\frac{3}{5}$
<=>$\frac{1}{3}$:x= $\frac{3}{5}$- $\frac{2}{3}$
<=> $\frac{1}{3}$:x= $\frac{-1}{15}$
<=>x=$\frac{1}{3}$ :$\frac{-1}{15}$
<=>x=$\frac{15}{-3}$
<=>x=-5
Chúc bạn học tốt!
