a: =>x+2/3=4/60=1/15
=>x=1/15-2/3=1/15-10/15=-9/15=-3/5
b: =>x/3=14/21-3/21=11/21
=>x=11/7
\(x+\dfrac{2}{3}=-\dfrac{1}{12}.\dfrac{-4}{5}.\\ \Leftrightarrow x+\dfrac{2}{3}=\dfrac{1}{15}.\\ \Leftrightarrow x=\dfrac{-3}{5}.\\ \dfrac{x}{3}=\dfrac{2}{3}+\dfrac{-1}{7}.\\ \Leftrightarrow\dfrac{x}{3}=\dfrac{11}{21}.\\\Leftrightarrow \dfrac{7x}{21}=\dfrac{11}{21}.\\\Leftrightarrow7x=11.\\ \Leftrightarrow x=\dfrac{11}{7}. \)
\(a,x+\dfrac{2}{3}=-\dfrac{1}{12}.\dfrac{-4}{5}=\dfrac{1}{15}\)
\(x=\dfrac{1}{15}-\dfrac{2}{3}=-\dfrac{3}{5}\)
\(b,\dfrac{x}{3}=\dfrac{2}{3}+\left(-\dfrac{1}{7}\right)=\dfrac{11}{21}\)
\(\dfrac{7x}{21}=\dfrac{11}{21}\)
\(x=\dfrac{11}{7}\)
