bonjour je suis en difficulté sur un exercice de 3ème a)7x=13 b)x-3=12 c)-x/3=5 d)3x+10=28 e)7-4x=11 f)9=2x+7 Merci beaucoup de votre aide

Bjr,

x = 13/7

x = 12 + 3 = 15

-x/3 = 5

-x = 15

x = - 15

3x + 10 = 28

3x = 28 - 10

3x = 18

x = 18/3 = 6

7 - 4x = 11

- 4x = 11 - 7

- 4x = 4

x = -4/4 = -1

2x + 7 = 9

2x = 9 - 7

2x = 2

x = 2/2 = 1

Réponse :

Explications étape par étape

Bonsoir

a)7x=13

7x/7 = 13/7

x = 13/7

[tex]\boxed{x = \dfrac{13}{7}}[/tex]

b)x-3=12

x - 3 + 3 = 12 + 3

x = 15

[tex]\boxed{x = 15}[/tex]

c)-x/3=5

-x/3 * (-3) = 5 * (-3)

x = -15

[tex]\boxed{x = -15}[/tex]

d)3x+10=28

3x + 10 - 10 = 28 - 10

3x = 18

3x/3 = 18/3

x = 6

[tex]\boxed{x = 6}[/tex]

e)7-4x=11

7 - 4x + 4x = 11 + 4x

7 - 11 = 11 + 4x - 11

-4 = 4x

-4/4 = 4x/4

x = -1

[tex]\boxed{x = -1}[/tex]

f)9=2x+7

9 - 7 = 2x + 7 - 7

2 = 2x

2x/2 = 2/2

x = 1

[tex]\boxed{x = 1}[/tex]