x+y=2
2x-y=2
складывая
3x=4
x=4/3
y=2-x
y=2-4/3=6/3-4/3=2/3
(4/3;2/3)
x=2-y
2*(2-y)-y=2
4-3y=2
3y=2
y=2/3
x=2-2/3=4/3