see what happen to the equation when and
| x - 3 | + | 3 - x | = 12
Either x-3 or 3-x will be positive. The other will be the negative of the other answer.
For example, if x=1,
You can prove this algebraicly by saying that:
Because you're taking the modulus of the answer, you'll end up with the same number twice.
|-2| = 2
|2| = 2
To get an answer of 12,
|x-3|=6 and |3-x|=6
x=9 or x=-3