if you do not know the salt, you would probably need to guess it and this guessing might be very difficult because salts are often both random and long.
Therefore, it depends on the algorithm, the randomness (and charset, different characters used for the salt) and the length of the salt to determine if the salt can be "guessed".
Sometimes you also have the hash and password and only miss the salt. In some cases like this you could just swap the role of the salt and password, i.e. the known password becomes your salt (something you know) and the salt becomes you password (something you want to discover).
There is no magic way of discovering the salt from the hash alone (without cracking the hash) ... it's not hidden somewhere and can't be extracted (otherwise why would we need to store the salt together with the hash, if it would be somehow extractable/computable from the hash ? It is not).
Therefore, it depends on the algorithm, the randomness (and charset, different characters used for the salt) and the length of the salt to determine if the salt can be "guessed".
Sometimes you also have the hash and password and only miss the salt. In some cases like this you could just swap the role of the salt and password, i.e. the known password becomes your salt (something you know) and the salt becomes you password (something you want to discover).
There is no magic way of discovering the salt from the hash alone (without cracking the hash) ... it's not hidden somewhere and can't be extracted (otherwise why would we need to store the salt together with the hash, if it would be somehow extractable/computable from the hash ? It is not).