a) $416 + ( x - 45 ) = 387$
$⇔ 416 + x - 45 = 387$
$⇔ x = 387 - 416 + 45$
$⇔ x = 16$
b) $11 - ( x + 84 ) = 97$
$⇔ 11 - x + 84 = 97 $
$⇔ -x = 97 - 84 - 11$
$⇔ -x = 2$
$⇔ x = -2$
c) $- ( x + 84 ) + 213 = -16$
$⇔ -x - 84 + 213 = -16$
$⇔ -x = -16 + 84 - 213$
$⇔ -x = -145$
$⇔ x = 145$
d) $x + ( - 35 ) = 18$
$⇔ x = 18 + 35$
$⇔ x = 53$
e) $-2x - ( -17 ) = 15$
$⇔ -2x + 17 = 15$
$⇔ -2x = 15 - 17 $
$⇔ -2x = -2$
$⇔ x = 1$
f) $3x + 27 = 9$
$⇔ 3x = 9 - 27 $
$⇔ 3x = -18$
$⇔ x = -6$
g) $2x + 12 = 3( x - 7 )$
$⇔ 2x + 12 = 3x - 21$
$⇔ 2x - 3x = -21 - 12$
$⇔ -x = -33$
$⇔ x = 33$
h) $2x.2 - 1 = 49$
$⇔ 4x - 1 = 49$
$⇔ 4x = 50$
$⇔ x = \dfrac{25}{2}$
i) $| -9 - x | - 5 = 12$
$⇔ | -9 - x | = 17$
⇔ \(\left[ \begin{array}{l}-9-x=17\\-9-x=-17\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=-26\\x=8\end{array} \right.\)
