Giải thích các bước giải:
a, $3x$ -$\dfrac{2}{3}$ =$\dfrac{-5}{9}$
⇔$3x$ =$\dfrac{-5}{9}$ +$\dfrac{2}{3}$
⇔ $x$ = $\dfrac{1}{9}$ : $\dfrac{3}{1}$ =$\dfrac{1}{9}$ .$\dfrac{1}{3}$
⇒ $x$ = $\dfrac{1}{27}$
Vậy x= $\dfrac{1}{27}$
b, $\dfrac{4}{5}$ -| $x$ +$\dfrac{1}{2}$ |=$\dfrac{1}{4}$
⇔ $x$ +$\dfrac{1}{2}$ = $\dfrac{4}{5}$ -$\dfrac{1}{4}$
⇔ $x$ +$\dfrac{1}{2}$= $\dfrac{11}{20}$
⇔ $x$ =$\dfrac{11}{20}$ -$\dfrac{1}{2}$= $\dfrac{11}{20}$ -$\dfrac{10}{20}$
⇔ $x$ = $\dfrac{1}{20}$
Vậy x= $\dfrac{1}{20}$