{3x+y= - 1
{ - x + 2y=12
3x+y= - 1 |* 2 =>
....................
6x+2y= - 2
-x+2y=12. ( -)
..........
7x= - 14 =>x=-14/7 =>x= - 2
-2 + 2y= 12 =>2y=14 =>y=14/2
y=7
=> x= - 2, y=7
