Ta có:
\(12-\left|x-3\right|=5x+8\)
TH1: \(\left|x-3\right|=x-3\)
\(\Rightarrow12-\left(x-3\right)=5x+8\)
\(\Rightarrow12-x+3=5x+8\)
\(\Rightarrow12+3-8=5x+x\)
\(\Rightarrow7=6x\Rightarrow x=\frac{7}{6}\)
TH2: \(\left|x-3\right|=-\left(x-3\right)=3-x\)
\(\Rightarrow12-\left(3-x\right)=5x+8\)
\(\Rightarrow12-3+x=5x+8\)
\(\Rightarrow12-3-8=5x-x\)
\(\Rightarrow1=4x\Rightarrow x=\frac{1}{4}\)