a) Ta có: \(\frac{x}{4}+\frac{9}{18}=\frac{7}{12}\)
\(\Leftrightarrow\frac{x}{4}=\frac{7}{12}-\frac{9}{18}=\frac{21}{36}-\frac{18}{36}=\frac{3}{36}=\frac{1}{12}\)
\(\Leftrightarrow x=\frac{4\cdot1}{12}=\frac{1}{3}\)
Vậy: \(x=\frac{1}{3}\)
b) Ta có: \(\left|2x-1\right|=\frac{9}{4}\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-1=\frac{9}{4}\\2x-1=-\frac{9}{4}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=\frac{9}{4}+1=\frac{13}{4}\\2x=-\frac{9}{4}+1=-\frac{5}{4}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\frac{13}{4}:2=\frac{13}{8}\\x=-\frac{5}{4}:2=-\frac{5}{8}\end{matrix}\right.\)
Vậy: \(x\in\left\{\frac{13}{8};-\frac{5}{8}\right\}\)
