To solve for X you first want to get all the terms that have an X in them to one side of the equation -- in this case the easiest way to do that is to subtract X/3 from both sides.
This leaves you with 1 = X/6 - X/3, so you didn't have to do anything with the 1.
The next step...
Since there aren't any restrictions placed on the nybbles each bit is not dependent on any other bit this is important because it means that:
The first digit in the nybble (the first bit) has two options -- either a 0 or 1
The second digit in the nybble (the second bit) also...
To use Gauss' approach split the numbers you want to add into two even groups. In this case you have 94 sequential numbers to add, so you will have two groups of 47. To make the method easier to visualize, write the first group with the numbers going up