a)
\(\begin{array}{l}15x = - 75\\x = \left( { - 75} \right):15\\x = - 5\end{array}\)
b)
\(\begin{array}{l}3\left| x \right| = 18\\\left| x \right| = 18:3\\\left| x \right| = 6\end{array}\)
Nên \(x = 6\) hoặc \(x = -6\)
Đáp số: a) \(x = -5\)
b) \(x = 6; x = -6\)
