$a. |2x + 1| - 19 = -7$
$⇔|2x + 1| = -7 + 19$
$⇔|2x + 1| = 12$
⇔\(\left[ \begin{array}{l}2x+1=12\\2x+1=-12\end{array} \right.\) ⇔ \(\left[ \begin{array}{l}x=\frac{11}{2}\\x=\frac{-13}2\end{array} \right.\)
$b. (-28) - 7 * |-3x + 15| = -70$
$⇔7 * |-3x + 15| = -28 + 70 = 42$
$⇔|-3x + 15| = 42 : 7 = 6$
⇔\(\left[ \begin{array}{l}-3x+15=6\\-3x+15=-6\end{array} \right.\) ⇔ \(\left[ \begin{array}{l}x=3\\x=7\end{array} \right.\)
