a) 2(x - 1) + 3(x - 2) = x - 4
2x - 2 + 3x - 6 = x - 4
5x - 8 = x - 4
5x = x - 4 + 8
5x = x + 4
5x - x = 4
4x = 4
Vậy x = 4
b) 3(4 - x) - 2(x - 1) = x + 20
12 - 3x - 2x + 2 = x + 20
14 - 5x = x + 20
14 - 5x - x = 20
14 - 6x = 20
14 - 20 = 6x
-6 = 6x
x = -6 : 6
x = -1
Vậy x = -1