X=y+10;
6(y+10)+7y-21=0;
6y+60+7y-21=0;
13y=-39;
y=-3;
x=-3+10=7;
(7;-3)
у+х=0
2х+у=-3
у+х=0/•(-1)
-у-х=0
-у-х+2х+у=0+(-3)
-х+2х=-3
х=-3
у+(-3)=0
-3у=0
у=0
X=y+10;
6(y+10)+7y-21=0;
6y+60+7y-21=0;
13y=-39;
y=-3;
x=-3+10=7;
(7;-3)
у+х=0
2х+у=-3
у+х=0/•(-1)
-у-х=0
2х+у=-3
-у-х+2х+у=0+(-3)
-х+2х=-3
х=-3
у+(-3)=0
-3у=0
у=0
х=-3
у=0