x^2+xy=6x
x^2+y^2=3(x+y)

x=4+y

(4+y)^2+y(4+y)=6 

x=4+y

16+8y+y^2+4y+y^2=6

x=6+y

2y^2+12y+10=0 I:2

x=6+y

y^2+6y+5=0

 x=6+y

y=1 и y=-5

x=7 и x=1 

y=1 и y=-5