$a, 6x + 8 = 2x - 12$
$6x - 2x = -12 - 8$
$4x = -20$
$x = -5$
$Vậy x = -5$
$b, 12 - x = x + 1$
$-x - x = 1 - 12$
$-2x = -11$
$x =$ `11/2`
$Vậy x =$ `11/2`
$c, 14 + 4x = 3x + 20$
$4x - 3x = 20 - 14$
$x = 6$
$Vậy x = 6$
$d, 2 ( x - 1 ) + 3 ( x - 2 ) = x - 4$
$2x - 2 + 3x - 6 = x - 4$
$5x - 8 = x - 4$
$5x - x = - 4 + 8$
$4x = 4$
$x = 1$
$Vậy x = 1$
$e, 3 ( 4 - x ) - 2 ( x - 1 ) = x + 20$
$12 - 3x - 2x + 2 = x + 20$
$14 - 5x = x + 20$
$-5x - x = 20 - 14$
$-6x = 6$
$x = -1$
$Vậy x = -1$
$f, 2 ( x - 3 ) - 3 ( x - 5 ) = 4 ( 3 - x ) - 1$
$2x - 6 - 3x + 15 = 12 - 4x - 1$
$-x + 9 = 11 - 4x$
$-x + 4x = 11 - 9$
$3x = 2$
$x =$ `2/3`
$Vậy x =$ `2/3`
