X+y+z=3 3y-x=21 2x+y+3z=-5

x + y + z = 3. | dikali3. | 3x+3y+3z = 9
2x+ y + 3z = 5. | dikali 1 | 2x+y+3z = 5
___________-
x + 2y = 4 .... pers. pertama

x + 2y = 4.
-x + 3y = 21.
_________+
5y = 25
y = 5


x + 2y = 4
x + 2.5 = 4
x = 4 - 10
x = -6

x+y+z =3
-6+5+z = 3
z = 3 +1
z = 4