Bài 7:
a) -5(x - 7) = 20
x - 7 = 20 : (-5)
x - 7 = -4
x = -4 + 7
x = 3
Vậy x = 3
b) -6|x - 2| = -18
|x - 2| = -18 : (-6)
|x - 2| = 3
⇔ \(\left[ \begin{array}{l}x - 2 = 3\\x - 2 = -3\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x = 3 + 2\\x = -3 + 2\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x = 5\\x = -1\end{array} \right.\)
Vậy x = 5 hoặc x = -1