Réponse:

1)

[tex]3x = 15 \\ < = > x = \frac{15}{3} = 5[/tex]

2)

[tex] - 5 - x = 4 \\ < = > - x = 9 \\ < = > - x \times ( - 1) = 9 \times ( - 1) \\ < = > x = - 9[/tex]

3)

[tex]3x + 4 = - 9 \\ < = > 3x = - 9 - 4 \\ < = > 3x = - 13 \\ < = > x = \frac{ - 13}{3} [/tex]

4)

[tex] - 10 - \frac{x}{4} = - 1 \\ < = > - \frac{x}{4} = - 1 + 10 \\ < = > - \frac{x}{4} = 9 \\ < = > - \frac{x}{4} \times 4 = 9 \times 4 \\ < = > - x = 36 \\ < = > x = - 36[/tex]