#4
1-x
2-y
{x=2y
{x-5/3=y-10/1
x=2y
x-5=3(y-10
x-5=3y-30
x-3y=-30+5
x-3y=-25
{x=2y
{x-3y=-25
2y-3y=-25
-y=-25(-1)
y=25
x=25*2
x=50
#4
1-x
2-y
{x=2y
{x-30/1=y+5/1,5
(x-30)*1,5=y+5
1,5x-45=y+5
1,5x-y=5+45
1,5x-y=50
{x=2y
{1,5x-y=50
1,5*2y-y=50
3y-y=50
2y=50:2
y=25
x=25*2
x=50