1.

x-2y=5

y=x/2-2.5

2x+3*(x/2-2.5)=3
3.5x-7.5-3=0
3.5x-10.5=0

x=10.5/3.5
x=3

3-2y=5

y=-2/2

y=-1

x^2+y^2=3^2+(-1)^2=9+1=10

2.

5x+2y=-3

y=-2.5x-1.5

x-3*(-2.5x-1.5)=-4 

8.5x+4.5+4=0

x=-8.5/8.5
x=-1

5*(-1)+2y=-3
-2+2y=0

y=2/2

y=1

x^2-y^2=(-1)^2-1^2=1-1=0

3.

3x-2y=1

y=1.5x-0.5

4x-(1.5x-0.5)=-2
2.5x+0.5+2=0 

x=-2.5/2.5
x=-1

3*(-1)-2y=1

y=-4/2
y=-2

y^2-x^2=(-2)^2-(-1)^2=4-1=3