bjr

les x à gauche - les constantes à droite

4x = 2

4x/4 = 2/4

x  = 2/4 = 0,5

x - 5 = 3

x - 5 + 5 = 3 + 5

x = 8

5x = 4x + 12

5x - 4x = 4x - 4x + 12

5x = 12

5x/5 = 12/5

x = 12/5 = 2,4

et

8y - 6y + 7 - 7 = 6y - 6y + 9 - 7

2y = 2

2y/2 = 2/2

y = 1