To find 'y', you must get it by itself in the equation. In order to do so, you need to get rid of other values on that side of the equation, while still making the expression equal the same. You need to "balance the equation". To do so, subtract 2 from both sides of the equation.
y + 2 = x
- 2 -2
y = x - 2
Your simplest answer for this problem would be y = x - 2
Hope this helps!