4-(5+y)+(7-2y)=4-5-y-7+2y
4+(5-y)-(7-2y)=4+5-y-7-2y

4-(5+у)+(7-2у)=4-5-y-7+2y4-5-y+7-2y=-8+y6-3y=-8+y4y=14y=14/4y=3,54+(5-y)-(7-2y)=4+5-y-7-2y4+5-y-7+2y=2-3y2+y=2-3yy+3y=2-24y=0y=0/4y=0