$a) 13 - | x | = | -4 |$
$⇒ 13 - | x | = 4$
$⇒ | x | = 13 - 4$
$⇒ | x | = 9$
$⇒\left[ \begin{array}{l}x=9\\x=-9\end{array} \right. $
$b) | x | - 3 + 6 = 16$
$⇒ | x | - 3 = 16 - 6 $
$⇒ | x | -3 = 10$
$⇒ | x | = 10 + 3$
$⇒ | x | = 13$
$⇒\left[ \begin{array}{l}x=13\\x=-13\end{array} \right.$
$c) 35 - | 2x - 1 | = 14$
$⇒ | 2x - 1 | = 35 - 14$
$⇒ | 2x - 1 | = 21$
$⇒\left[ \begin{array}{l}| 2x - 1 | = 21\\| 2x - 1 | = -21\end{array} \right.$
$⇒\left[ \begin{array}{l}x=20\\x=-11\end{array} \right.$
$d) | 3x - 2 | + 5 = 9 - x$
$⇒ | 3x - 2 | = 4 - x$
$⇒ 3x - 2 = 4 - x$ hoặc $3x - 2 = x - 4$
$⇒ 3x + x = 4 + 2$ hoặc $3x - x = -4 + 2$
$⇒ 4x = 6$ hoặc $2x = - 2$
$x = 1,5$ hoặc $1$
$⇒ x ∈ Z$ nên $x = -1$
