Question 904088
If you solve x+y+z=1 for z, then you get


x+y+z=1


y+z=1-x


z = 1-x-y


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Plug this into the second equation


2x+4y+2z=-4


2x+4y+2(1-x-y)=-4


2x+4y+2-2x-2y=-4


2y+2 = -4


2y = -4-2


2y = -6


y = -6/2


y = -3



Because z = 1-x-y, and y = -3, we know that z = 1-x-y turns into z = 1-x-(-3) and that simplifies to z = 4-x


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Now turn to the third equation -x+7y-3z=-35 



-x+7y-3z=-35 


-x+7y-3(4-x)=-35 ... plug in z = 4-x


-x+7y-12+3x=-35


-x+7(-3)-12+3x=-35 ... plug in y = -3, now solve for x


-x-21-12+3x=-35


2x-33 = -35


2x = -35+33


2x = -2


x = -2/2


x = -1


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z = 4 - x


z = 4 - (-1)


z = 4 + 1


z = 5


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Summary: 


x = -1
y = -3
z = 5


The solution as an ordered triple is (-1,-3,5)