besoin d'aide exercice avec les equations il faut séparé le x des chiffres

1)
2x - 5 = 21
2x = 21 + 5
2x = 26
x = 26/2
x = 13

2)
4x + 9 = - 11
4x = - 11 - 9
4x = - 20
x = - 20/4
x = - 5

3)
9x + 10 = 3x - 2
9x - 3x = - 2 - 10
6x = - 12
x = -12/6
x = - 2

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