Explanation:
what do we need to do ?
just solve the system of 2 equations ?
as we have x and -x in the equations, we simply add both equations, get one summary equation just in y, solve for y, and then use one of the original equations to solve for x :
y = x - 4
y = -x + 2
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2y = 0 - 2
2y = -2
y = -1
-1 = x - 4
3 = x
x = 3
y = -1