Bonjour,
x² +6x -4x -24 = x²+3x
x² +6x -4x -x² -3x = 24
-x = 24
x= -24
5x-7 = -3
5x = -3+7
5x = 4
x= 4/5
3x+2 = -7x +9
3x+7x = 9-2
10x = 7
x= 7/10