besoin d'aide svp pour l'exercice 1 , 2 et 3

bonjour

Exercice I

5 x ( - 4 x +12) = - 20 x² + 60

-6 ( 3 y +15) = - 18 y - 90

5 x +3 ( - 6x +10) - 20 = 5 x - 18 x + 30 -20 = - 13 x + 10

Exercice II
3 x +5 = 7 x -4
3 x - 7 x = - 4 -5
- 4 x = -9
x = 9/4

10 x = 2 x +7
10 x - 2 x = 7
8 x = 7
x = 7/8

- 4 x + 7 = 3 x -10
- 4 x - 3 x = - 10 -7
- 7 x = - 17
x = 17/7

32 = 5 x + 18
32  -18 = 5 x
14 = 5 x
x = 14/5

7 x +28  = 7 ( x + 4)
9 x² +12 = 3 ( 3 x² +4)
13 x² - 7 x = x ( 13 x - 7)
4( x +2) - 8 x ( x +2) = ( x +2) ( 4 - 8 x ) 

Exercice III
calcul de Charlotte
8 x  +7
calcul de Arthur
10 x -2

8 x +7 = 10 x -2
8 x - 10 x = - 2 -7
- 2x = -9
x = 9/2 = 4,5

ils ont choisi 4, 5