The most important thing to remember about rearranging equations is that what you do to one side, you have to do to the other side as well to balance it. In the question above, to get rid of the 2 on the right hand side of the equation we must subtract 2. This then means we must also subtract 2 from the left side of the equation. This would give us:
y - 2 = 3x + 2 - 2
Which can then be simplified to:
y - 2 = 3x
Then we divide the RHS of the equation by 3 to leave just x, and then divide by 3 on the LHS to balance.
This would give us our answer of:
(y-2)/3 = x