1.
{2x-3y=5
{x-6y=-2 => x=-2+6y
2(-2+6y)-3y=5
-4+12y-3y=5
9y=9
y=1
x=4
2.
{2x-3y=11
{5x+y=2 => y=2-5x
2x-3(2-5x)=11
2x-6+15x=11
17x=17
x=1
y=-3
3.
{x²-3y=22
{x+y=2 => x=2-y
(2-y)²-3y=22
4-4y+y²-3y-22=0
y²-7y-18=0
y₁+y₂=7
y₁*y₂=-18
y₁=9; x₁=-7
y₂=-2; x₂=4
4.
{x+y=4 => y=4-x
{x²-4y=5
x²-4(4-x)=5
x²-16+4x-5=0
x²+4x-21=0
x₁+x₂=-4
x₁*x₂=-21
x₁=-7; y₁=11
x₂=3; y₂=1