1
{3x+y=-3
{-5x+y=7
-------------------
-2x=4
x=-2
-6+y=-3
y=3
(-2;3)
2
{2y-x=-8
{4y+x=-4
--------------
6y=-12
y=-2
-8+x=-4
x=4
(4;-2)
3
{4y-3x=11
{2y+3x=1
------------------
6y=12
y=2
4+3x=1
3x=-3
x=-1
(-1;2)
4
{5x-4y=7
{3x+4y=-15
----------------
8x=-8
x=-1
-3+4y=-15
4y=-12
y=-3
(-1;-3)