{2x+y=7;
{x(7-2x)-x=4,
{y=7-2x;
{7x-2x^(2)-x-4=0,
{y=7-2x;
{-2x^(2)+6x-4=0,
{y=7-2x;
{x^(2)-3x+2=0,
{y=7-2x;
{x=1,........... или ..... .. {x=2,
{y=7-2x;.......................{y=7-2x;
{x=1,...............................{x=2,
{y=5;...............................{y=3.
Ответ: (1; 5), (2; 3).