b.
\(\left|5x+3\right|=\left|x+2\right|\)
\(\Leftrightarrow\left[{}\begin{matrix}5x+3=x+2\\5x+3=-x-2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}5x-x=2-3\\5x+x=-2-3\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}4x=-1\\6x=-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{4}\\x=\dfrac{-5}{6}\end{matrix}\right.\)