3)
a) 7x + 49 = 28
7x = 28 - 49
7x = -21
x = -21 : 7
x = -3
Vậy x = -3
b) -3/2 + 5/2 x = 7/2
5/2 x = 7/2 + 3/2
5/2 x = 5
x = 5 : 5/2
x = 2
Vậy x = 2
c) 1/3 - 1/6 x = 1
1/6 x = 1/3 - 1
1/6 x = -2/3
x = -2/3 : 1/6
x = -4
Vậy x = -4
d) -7/4 - 3/2 x = 3/8
3/2 x = -7/4 - 3/8
3/2 x = -17/8
x = -17/8 : 3/4
x = -17/6
Vậy x = -17/6
e) (x - 1)/4 = (2x + 1)/10
5(x - 1) = 2(2x + 1)
5x - 5 = 4x + 2
5x - 4x = 2 + 5
x = 7
Vậy x = 7