Write an absolute value equation that has the given solutions 3 and 9

The absolute value of the a certain number is the positive equivalent of the number. 

Example,
The absolute value of 3, expressed as I3I is 3. Also,
the absolute value of -3, expressed as I-3I is 3. 

For this item, we have the equation,
              Ix - 6I = 3

If we substitute 3 to x, we have,
             I3 - 6I = I-3I = 3
Also, if we substitute 9 to the equation,
            I9 - 6I = I3I = 3

Thus, we can have the equation as given above,
          Ix - 6I = 3
as the answer.

It is to be noted that there are still other equations that can be used as answer to this item. 

Whose mistake? can you give more details to what the question is asking?