-y = x + 3 . . . . this is the sides for the double lines
2y + 24 = x + 9 . . . . this is the sides for the single lines
To solve you need to substitute one equation into the other
-y = x + 3
y = -x - 3 . . . place this equation into the other equation where (Y) is
2y + 24 = x + 9
2 ( -x - 3) + 4 = x +9
-2x - 6 + 24 = x + 9
-2x +18= x+9
-3x = -9
x = 3 . . . substitute this answer into the equation and solve for (Y)
-y = x + 3
- y = 3 +3
-y = 3 + 3
y= -6
