Explanation

(b)
$2x - 1 = |x + 7| = \left\{ \begin{matrix}
x + 7,if\ x \geq - 7 \\
- (x + 7),if\ x < - 7
\end{matrix} \right.\$
$\therefore If\ x \geq - 7,\ 2x - 1 = x + 7 \Rightarrow x = 8$
If $x < - 7,\ 2x - 1 = - (x + 7)$
$\Rightarrow 3x = - 6$
$\Rightarrow x = - 2,\$which is not possible