a, $\frac{2}{3}$ + $\frac{5}{3}$ .x= $\frac{5}{7}$
$\frac{5}{3}$.x= $\frac{5}{7}$ + $\frac{2}{3}$
$\frac{5}{3}$ .x= $\frac{1}{21}$
x = $\frac{1}{21}$ : $\frac{5}{3}$
x= $\frac{1}{35}$
Vậy x= $\frac{1}{35}$
b, $\frac{1}{2}$ .(x- $\frac{1}{3}$ )+ $\frac{-1}{2}$ = $\frac{3}{4}$
$\frac{1}{2}$ .(x- $\frac{1}{3}$ ) = $\frac{3}{4}$ - $\frac{-1}{2}$
$\frac{1}{2}$ .(x- $\frac{1}{3}$ ) =$\frac{5}{4}$
x-$\frac{1}{3}$ =$\frac{5}{4}$:$\frac{1}{2}$
x-$\frac{1}{3}$ = $\frac{5}{2}$
x = $\frac{5}{2}$+$\frac{1}{3}$
x = $\frac{17}{6}$
Vậy x= $\frac{17}{6}$
CHÚC BẠN HỌC TỐT!!!
