a: \(\dfrac{2}{3}:0.1x=\dfrac{4}{3}:\dfrac{4}{5}=\dfrac{4}{3}\cdot\dfrac{5}{4}=\dfrac{5}{3}\)
\(\Leftrightarrow x\cdot\dfrac{1}{10}=\dfrac{2}{3}:\dfrac{5}{3}=\dfrac{2}{5}\)
\(\Leftrightarrow x=\dfrac{2}{5}:\dfrac{1}{10}=\dfrac{2}{5}\cdot10=4\)
b: |x-3|=1/2
=>x-3=1/2 hoặc x-3=-1/2
=>x=7/2 hoặc x=5/2