Salut,

3x = 9

x= 9/3 = 3

5y = 3

y = 3/5 = 0,6

4z = -7

z = -7/4 = -1, 75

-2z = -8

z = -8/(-2) = 4

7x = 4

x = 4/7

- y = - 7,2

y = 7, 2

- y = 15,7

y = -15, 7

4,4z = 0

z = 0/4, 4 = 0

2,7x = -1, 2

x= -1, 2/2, 7

J'espère t'avoir aidé !

Dreamus