None of the given equation has at least one solution
1) -8x + 2 = -8x - 4 ⇒ no
2) 12 - x = 5x + 12 ⇒ no
3) 6x + 9 = 6x + 9 ⇒ no
4) 15 - x = 10 - x ⇒ no
Solution:
1) -8x + 2 = -8x - 4
In the above equation, -8x gets cancel each other on both sides
-8x + 2 = -8x - 4

There is no value of x that will ever make this a true statement, the solution to the equation above is “no solution”
2) 12 - x = 5x + 12
In the above equation, 12 gets cancel each other on both sides
-x = 5x

There is no value of x that will ever make this a true statement, the solution to the equation above is “no solution”
3) 6x + 9 = 6x + 9
In the above equation, 6x + 9 gets cancel each other on both sides
There is no value of x that will ever make this a true statement, the solution to the equation above is “no solution”
4) 15 - x = 10 - x
In the above equation, -x gets cancel each other on both sides

There is no value of x that will ever make this a true statement, the solution to the equation above is “no solution”