2x-3y= 1.......(2)
(1) into (2):
2x-3(x-7)= 1
2x-3x+2 1= 1
-x=-20
x=20
Replace (1):
y=20-7= 13
(2) y=-x+2....( 1)
y=x- 1............(2)
( 1)-(2):
0=-x+2-x+ 1
2x=3
x=3/2
Replace (1):
y=-3/2+2= 1/2
(3) y-2x=-3...( 1)
2x+2y=8.......(2)
( 1)+(2):
y+2y=-3+8
3y=5
y=5/3
Substitution into (2):
2x+2(5/3)=8
2x=8- 10/3
x=7/3
(4) x-y- 1=0...( 1)
4(x-y)-y=5.....(2)
From ( 1): X-Y = 1
Substitution into (2):
4× 1-y=5
y=- 1
Replace (1):
x-(- 1)- 1=0
x=0
(5) 2y+x=5....( 1)
x-y=2.............(2)
( 1)-(2):
2y+y=3
y= 1
Replace (1):
2× 1+x=5
x=3
(6) 7y+4x= 19..( 1)
4x= 17+5y.......(2)
( 1)-(2):
7y= 19- 17-5y
12y=2
y= 1/6
Substitution into (2):
4x= 17+ 1/6×5
4x= 107/6
x= 107/24
(7) x+2y= 1 1....( 1)
3x-2y= 1 1.........(2)
( 1)+(2):
x+3x = 1 1+ 1 1
4x=22
x= 1 1/2
Replace (1):
1 1/2+2y = 1 1
1 1+4y=22
4y= 1 1
y= 1 1/4
(8) |x-2y- 1|+(2x-y-5)^2=0
x-2y- 1=0.......( 1)
2x-y-5=0.......(2)
( 1)-(2)×2:
x-2y- 1-(4x-2y- 10)= 0
-3x+9=0
x=3
Substitution into (2):
2×3-y-5=0
y= 1