Cau 2:
\(a,\Rightarrow\dfrac{3}{7}x=\dfrac{1}{3}\Rightarrow x=\dfrac{7}{9}\\ b,\Rightarrow x=\dfrac{-16.15}{20}=-12\\ c,\Rightarrow\left|x-\dfrac{2}{5}\right|=2,25=\dfrac{9}{4}\\ \Rightarrow\left[{}\begin{matrix}x=\dfrac{9}{4}+\dfrac{2}{5}=\dfrac{53}{20}\\x=-\dfrac{9}{4}+\dfrac{2}{5}=-\dfrac{37}{20}\end{matrix}\right.\\ d,\Rightarrow x+\dfrac{1}{2}=-\dfrac{7}{4}\Rightarrow x=-\dfrac{9}{4}\)