On a number line, v would be all the numbers to the left of -3 (for example, |-4|=4 which is greater than 3) and all the values to the right of positive 3. Since it can't equal 3, v=-3 and v=3 are not included on the number line.
you need the x alone so you substract 3 from both sides.
Then you have, -x= -12
You need the x positive so you change the sign for it but as it is an equation you need to do the same thing on the other side, making both sides positive.