There are infinitely many solutions
4(x - 3) = 4x - 12
4x - 12 = 4x - 12
+ 12 + 12
4x = 4x
-4x -4x
0 = 0
When your answer is equal on both sides, that means that there are infinite solutions. In other words, they are the same line. This means that they share all of the same points, which are infinite.
Hope this helps!