Calculer x dans chaque cas :x+4=7;4x+8=12;-6x+18=30;18x=21

bonsoir =)

x + 4 = 7
x = 7-4
x = 3


4x + 8 = 12 
4x = 12 -8 
4x = 4 
x = 4/4
x = 1

-6x + 18 = 30
-6x = 30 - 18
-6x = 12
x = 12/-6
x = -2

18x=21
x = 21/18
x= 7/6

x+4 = 7             4x + 8 = 12       -6x + 18 = 30       18x = 21
x = 7 - 4            4x = 12 - 8        -6x = 30 - 18        x = 21/18 = 7/6
x = 3                 4x = 4               -6x = 12
                         x = 4/4 = 1       x = 12/-6 = -2