x+y-z=1 8x+3y-6z=1 -4x-y+3z=1

x + y - z = 1 
-----------------x8
8x + 8y - 8z = 8

-4x - y + 3z = 1 
---------------------x2
-8x - 2y + 6z = 2

8x + 8y - 8z = 8
8x + 3y - 6z = 1
---------------------- --
5y - 2z = 7

8x + 3y - 6z = 1
-8x - 2y + 6z = 2
------------------------ +
y = 3

5(3) - 2z = 7
15 - 2z = 7
2z = 8
z = 4

x + y - z = 1
x + 3 - 4 = 1
x = 1 - 3 + 4
x = 2

Jadi, (x, y, z) = (2, 3, 4)