qui peut m'aider pour l'exercice 1 svp

bonjour
x +5 = 9
x = 9 - 5
x = 4
x - 4 = 13
x = 13 + 4
x = 17
- 7 = x - 3
- x = - 3 + 7
- x = 4
x = - 4
7 x = 21
x = 3
- 3 x = 12
x = - 4
5 x = - 3
x = - 3 /5