Answer :
x+y=2 (label equation one)
x-y=4 (label equation two)
y=-x+2 (equation one rearranged, label this equation equation three)
sub 3 into 2
x-(-x+2)=4
x+x-2=4
2x-2=4
2x=6
x=3
sub x=3 into equation one
3+y=2
y=-1
therefore x=3 and y=-1
x-y=4 (label equation two)
y=-x+2 (equation one rearranged, label this equation equation three)
sub 3 into 2
x-(-x+2)=4
x+x-2=4
2x-2=4
2x=6
x=3
sub x=3 into equation one
3+y=2
y=-1
therefore x=3 and y=-1