x+y=4
x-y=2
x+y=4
x-y=2
x = 4 - y
Substitute that value for x in the next equation.
4 - y - y = 2
2 = 2y
1 = y
Now substitute 1 for y in the first equation.
x-y=2
x-y=2
x = 4 - y
Substitute that value for x in the next equation.
4 - y - y = 2
2 = 2y
1 = y
Now substitute 1 for y in the first equation.