2х-у=-8
-у=-8-2х
у=8+2х
-0.8х-(0.6х-0.7(8+2х))=-0.8х-(0.6х-5.6-1.4х)=-0.8х-0.6х+5.6+1.4х=-1.4х+5.6+1.4х=5.6
2х-у=-8
-у=-8-2х
у=8+2х
-0.8х-(0.6х-0.7(8+2х))=-0.8х-(0.6х-5.6-1.4х)=-0.8х-0.6х+5.6+1.4х=-1.4х+5.6+1.4х=5.6