`d) x - 15 = - 21`
`⇔ x = - 21 + 15`
`⇔ x = - 6`
`e) 12 - ( 25 - x ) = 7`
`⇔ 25 - x = 12 - 7`
`⇔ 25 - x = 5`
`⇔ x = 25 - 5`
`⇔ x = 20`
`f) | x - 3 | = 5`
`⇔` \(\left[ \begin{array}{l}x - 3 = 5\\x - 3 = - 5\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x = 8\\x = - 2\end{array} \right.\)
`g) 42 - x = - 7`
`⇔ x = 42 - ( - 7 )`
`⇔ x = 49`
`k) | x | - 5 = 12`
`⇔ | x | = 12 + 5`
`⇔ | x | = 17`
`⇔` \(\left[ \begin{array}{l}x = 17\\x = - 17\end{array} \right.\)
`m) 1^5 + | x + 2 | = 8`
`⇔ 1 + | x + 2 | = 8`
`⇔ | x + 2 | = 8 - 1`
`⇔ | x + 2 | = 7`
`⇔` \(\left[ \begin{array}{l}x + 2 = 7\\x + 2 = -7\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x = 5\\x = - 9\end{array} \right.\)
