linea combination
combine them to elimiante a vairable
elimiante y's
multily 2nd equation by -1 to get x-y=-1
add that to first one
2x+y=4
1x-y=-1 +
3x+0y=3
3x=3
divide both sides by 3
x=1
sub back
x-y=-1
1-y=-1
minus 1 both sides
-y=-2
times -1
y=2
(x,y)
(1,2)
