Đáp án đúng: B Giải chi tiết:\(\begin{array}{l}\,5.x + 12 = 8\\\,\,\,\,\,5.x\,\,\,\,\,\,\,\,\,\,\,\, = 8 - 12\\\,\,\,\,\,5.x\,\,\,\,\,\,\,\,\,\,\,\, = - 4\\\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{ - 4}}{5}\,\,\,\,\,\,\end{array}\) Chọn B