ou sinon :

a) 5(x -2) = 2x + (x+6)

 5x - 10 = 2x + x + 6

5x -2x -x = 10 + 6

 2x = 16

x = 8

b) 12 - (5x - 9) = 4x + 3

12 - 5x + 9 = 4x + 3

-5x -4x = -12 - 9 +3

-9x = -18

x = 2

c) 5 +3 (2x + 2) = 6 - 4 (x + 1)

5 + 6x + 6 = 6 - 4x - 4

6x + 4x = -5 - 6 + 6 -4

10x = -9

x = -0,9

bonne chance ! :)