Je n’arrive pas l’exercice 90 j’ai besoin d’aide svp

bonjour

2 x + 1 = 13

2 x = 13 - 1

2 x = 12

x = 6

14 = 20 - 3 x

14 - 20 = - 3 x

- 6 = - 3 x

x  = 3/6 = 1/2

2 x + 1/7 = 1

2 x = 1 - 1/7

14 x /7 = 7/7 - 1 /7

14 x = 6

x = 6/14 =  3/7

3 x - 5 = 2 x + 10

3 x - 2 x = 10 + 5

x = 15

10 x + 3 = 7 x - 1

10 x - 7 x = - 1 - 3

3 x = - 4

x = - 4/3

3 x = 8 x +  15

3 x - 8 x = 15

- 5 x = 15

x = - 3