Réponse :
a) 2x + 6= 20
2x = 20 - 6
2x = 14
x = 14/2
x = 7
b) 7x - 4 = 10
7x = 10 + 4
7x = 14
x = 14/7
x = 2
c) 5x - 3 = 6 - 3x
5x = 6 - 3x + 3
5x = -3x + 9
5x + 3x = 9
8x = 9
x = 9/8
d) 3(5 - 2x) = 7 - 4x
3*5 + 3*(-2x) = 7 - 4x
15 - 6x = 7 - 4x
-6x = 7 - 4x - 15
-6x = -4x - 8
-6x + 4x = -8
-2x = -8
x = -8/-2
x = 4
J'espère t'avoir aidé !