Respuesta :

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