Răspuns:
x-2y=5
y+3z=7
3z+3y+x=12
1z+1y=12-x
1z+1y=12-7
1z+1y=5
x=12-5
x=7
7-2y=5
y=1
1+3z=7
z=2
x+6z=7+12=19.
