Not to be obvious, but you cannot shrink a snapshot. Taking a new snapshot does not shrink it, it creates a new snapshot with a new and update view of the data. Even if the answer appears to be about shrinking a snapshot, there is really nothing you can do and still keep the same view of the database. I do not feel this was a trick question, just don't be too quick to jump to a conclusion. Taking a new snapshot and deleting the old one could have huge ramifications and I would not want a DBA just immediately jumping down that path. Explaining all the options and the results of each option would be a better solution... but the immediate answer is that you cannot backup a snapshot.

David