Bonjour:
1) 3x + 4 = -7 - 2x
<=> 3x + 2x = -7 - 4
<=> 5x = -11
<=> x = [tex]\frac{-11}{5\\}[/tex]
2) 3x + 4 = 4x - 1
<=> 3x - 4x = -1 - 4
<=> -x = -5
<=> x = 5
3) 13x - 30 = 7x - 14
<=> 13x - 7x = -14 + 30
<=> 6x = 16
<=> x = [tex]\frac{16}{6}[/tex] = [tex]\frac{8}{3}[/tex]
4) 2(x+1) + 3(x-1) = 0
<=> 2x + 2 + 3x - 3 = 0
<=> 5x - 1 = 0
<=> 5x = 1
<=> x = [tex]\frac{1}{5\\}[/tex]
Voilà !
