Solve by substitution:

-x-y-z=-8
-4x+4y+5z=7
2x+2z=4

1 answer

multiply the first one by - 2
2 x + 2 y + 2 z = 16
from the last one substitute 4 for 2x+2z
2 y + 4 = 16
y = 12/2 = 6
now go back for the rest :)