You did not include instructions but I think you want to solve for y.
To do so, we isolate y.
Add 4 from both sides as step 1.
-y - 4 + 4 = 12 + 4
On the left side, -4 and +4 cancel out.
We now have this:
-y = 16
Next, divide both sides by -1.
Final answer: y = -16