[tex]\displaystyle\bf\\\left \{ {{\dfrac{y-3x}{7} =0}|\cdot 7 \atop {5x-y=6}} \right. \\\\\\+\left \{ {{-3x+y=0} \atop {5x-y=6}} \right. \\---------\\2x=6\\\\x=3\\\\y=3x=3\cdot 3=9\\\\Otvet \ : \ x= 3 \ \ , \ \ y=9[/tex]