Split into separate equations:
x=11, so we can reduce the other equations:
y-2z=11
4-121y+z=11, because 4-x2y+z=11
1-11+y+3=11, because 1-x+y+3=11, y=11+11-1-3=18, now we can find z:
18-2z=11, because y-2z=11, z=7/2.
But 4-121×18+7/2≠11, so the equations are inconsistent, therefore there is no solution, or the question has been misstated.
If the first equal sign in the compound equation had been either + or -, then we would arrive at x=-7.3, y=-0.3, z=-9 approx. This involves solving a cubic equation, and is unlikely to be the expected answer, so the question needs to be correctly stated.
Could this be the question? (for example)
(1) x-y-2z=4
(2) -x+2y+z=1
(3) -x+y-3z=11
(4)=(1)+(2)=y-z=5
(5)=(1)+(3)=-5z=15, z=-3.
From (4), y=5+z=5-3=2 and from (1), x-2+6=4, x=0.
SOLUTION: x=0, y=2, z=-3