2х+2у+z=12 |*3
3х+3у-5z=5 |*2
3z=36
-10z=10
13z=26
z=2
2x+2y+2=12
2x+2y=10
x+y=5
x+y-10z=5-2*10 = -15
2х+2у+z=12 |*3
3х+3у-5z=5 |*2
3z=36
-10z=10
13z=26
z=2
2x+2y+2=12
2x+2y=10
x+y=5
x+y-10z=5-2*10 = -15