|-2,5x|=x-12

* Hướng dẫn giải

Với $x\ge 0\Rightarrow \left(15\right)\iff \mathrm{2,5}x=x-12\iff x=-8\left(ktm\right)$

$+)x<0\Rightarrow \left(15\right)\iff -\mathrm{2,5}x=x-12\iff x=\frac{24}{7}(ktm)$

$S=\varnothing$Vậy