1) -5 + x = 3
x = 3 + 5
x = 8
2) -3 + 5x = 12 + 3x
5x - 3x = 3 + 12
2x = 15
x = 7,5
3) (x - 2) + (7x - 9) = 0
x - 2 = 0
x = 0 + 2
x = 2
7x - 9 = 0
7x = 0 + 9
7x = 9
x = 9/7
S = { 2 ; 9/7 }
4) 2 (2x + 1) = 3 (x - 4)
2 * 2x + 2 * 1 = 3 * x + 3 * (-4)
4x + 2 = 3x - 12
4x - 3x = -2 - 12
x = -14