a) \(4.\left|3x-1\right|+\left|x\right|-2.\left|x+5\right|+7.\left|x-3\right|=12\)
\(\Rightarrow4.\left(3x-1\right)+x-2.\left(x+5\right)+7.\left(x-3\right)=12\)
\(\Rightarrow12x-4+x-2x-10+7x-21=12\)
\(\Rightarrow12x-4+x-2x-10+7x-21-12=0\)
\(\Rightarrow18x-47=0\)
\(\Rightarrow18x=47\)
\(\Rightarrow x=47:18\)
\(\Rightarrow x=\frac{47}{18}\)
Vậy \(x=\frac{47}{18}.\)
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