Grammatically, this would not change X. "...GIVING X" would just return X. Since it's part of the same statement, it seems it should ignore the "ADD 5 TO X" part.
Now, if you'd like to place the result into X, I suggest "ADD 5 TO X" would suffice as the entire statement.
I kid, of course, but "X is x + 5" brings Prolog to mind with all the unification and bidirectionality that implies.