[tex]2x + y + z = 4 \\ 3x - y + 2 = - 5 \\ x + 2y + 2z = 5[/tex]

3x - y + 2z = -5
x+ 2y + 2z =5
------------------(-) elminasi
2x - 3y = -10
simpen aja
~~~~~~~`
4x + 2y +2z = 8
x + 2y +2z =5
--------------(-) eliminasi lagi
3x = 3
x= 1
sampe sini simpen lagi dan mulai substitusi
2(1) - 3y = -10
-3y = -12
y= 4
substitusi lagi paling enak ambil 2x+y+z=4
2(1) + 1(4) + z = 4
6+z=4
z= (-2)
jadi 
x= 1
y=4
z= (-2)