a)  On the number line, "x" is to the left from -9.

        Then it is clear that THERE IS NO solution in this case.

         (It is OBVIOUS, so I will not try to prove it).



b)  On the number line, "x" is between  -9 and 3.

        Then the distance from -9 to 3 is 12 units, and we should divide it in proportion 2:1, counting from left to right.


        Obviously, the point x= -1 divide the segment [-12,3] in this proportion.

        So, x= -1 is the solution in this case.



c)  On the number line, "x" is to the right from 3.


        Again, recall that the distance from -9 to 3 is 12 units;

        so, we need move 12 units to the right from 3; then we get x= 3+12 = 15.

        Thus x= 15 is the solution in this case.


ANSWER.  The problem has two solutions:  x= -1  and  x= 15.