it would be so much easier with elimination but ok
1.
x+y=1
minus x
y=1-x
sub
2x-(x-1)=-2
2x-x+1=-2
x+1=-2
x=-3
sub
y=1-x
y=1-(-3)
y=1+3
y=4
(-3,4)
2.
x-2y=2
add 2y
x=2y+2
sub
5(2y+2)-3y=-11
10y+10-3y=-11
7y+10=-11
7y=-21
y=-3
sub
x=2y+2
x=2(-3)+2
x=-6+2
x=-4
(-3,-4)
3.
x-y=3
add y
x=y+3
sub
6(y+3)+4y=13
6y+18+4y=13
10y+18=13
10y=-5
y=-1/2
sub
x=y+3
x=-1/2+3
x=5/2
(5/2,-1/2)
1. (-3,4)
2. (-3,-4)
3.(5/2,-1/2)
