1)
{ x-3y = 1 {x = 1+3y
{2xy-x²+9y² = 11-4x { 2(1+3y)*y-(1+3y)²+9y² = 11-4(1+3y);
2+6y*y-(1+6y+9y²)+9y² = 11-4-12y;
2+6y-1-6y-9y²+9y² = 7-12y;
1 = 7-12y;
-12y = 1-7;
-12y = -6;
y = -6:(-12);
y = 0,5.
----------
x-3*0,5 = 1;
x-1,5 = 1;
x = 1+1,5;
x = 2,5.
Ответ: (2,5; 0,5) или x=2,5, y=0,5.