the answer gzzydyyxggxggxxghyzyxycycgcycyc

Step-by-step explanation:
we start with the first and the third equations, as they have the same content structure.
we multiply the whole first equation by 2, so that the z terms become aligned, and then we add both equations :
-8x + 4z = 28
-2x - 4z = 22
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-10x + 0 = 50
x = -5
-2x - 4z = 22
-2×-5 - 4z = 22
10 - 4z = 22
-4z = 12
z = -3
y = x + z + 12
y = -5 - 3 + 12 = 4