Very (VERY!) rough, your gain or loss on the sale of rental property is determined as follows.
What you paid for the property, plus what you paid for any property improvements during the time you owned it, gives you your cost basis in the property.
Now subtract the total of all depreciation taken while you owned it, from your cost basis. This gives you your intermediate cost basis in the property.
Now add all of your carry forward losses to the intermediate cost basis, and that gives you your adjusted cost basis.
Note that this is an extremely rough method to see if you have a gain or a loss, and it's not perfect by any means.
Now if you sold the property for less than your adjusted cost basis, you have a loss.
If you sold the property for more than your adjusted cost basis, you have a gain.
So using this rough method, do you have a loss or a gain?
