Đáp án đúng: B
Giải chi tiết:\(\begin{array}{l}\left( {\left| x \right| + 3} \right).15 - 5 = 70\\\,\,\,\,\,\,\,\left( {\left| x \right| + 3} \right).15 = 70 + 5\\\,\,\,\,\,\,\,\left( {\left| x \right| + 3} \right).15 = 75\\\,\,\,\,\,\,\,\,\,\left| x \right| + 3 = 75:15\\\,\,\,\,\,\,\,\,\,\left| x \right| + 3 = 5\\\,\,\,\,\,\,\,\,\,\left| x \right| = 5 - 3\\\,\,\,\,\,\,\,\,\,\left| x \right| = 2\end{array}\)
Suy ra \(x = 2\) hoặc \(x = - 2\).
Vậy \(x \in \left\{ { - 2;2} \right\}\).
Chọn B.