Bonjour,
[tex]12x + 15 = 6x + 3[/tex]
[tex]12x - 6x = 3 - 15[/tex]
[tex]6x = - 12[/tex]
[tex]x = - \frac{12}{6} [/tex]
[tex]x = - 2[/tex]
[tex]5x - 3 = 2x + 4[/tex]
[tex]5x - 2x = 4 + 3[/tex]
[tex]3x = 7[/tex]
[tex]x = \frac{7}{3} [/tex]
[tex] - 7x - 8 = - 10x + 4[/tex]
[tex]10x - 7x = 8 + 4[/tex]
[tex]3x = 12[/tex]
[tex]x = \frac{12}{3} [/tex]
[tex]x = 4[/tex]
[tex]2x + 7 = 9x - 5[/tex]
[tex]9x - 2x = 7 + 5[/tex]
[tex]7x = 12[/tex]
[tex]x = \frac{12}{7} [/tex]