Answer:
There is one knave
Step-by-step explanation:
Let's analyze the two possible scenarios, from the unheard Fred's answer
- SCENARIO 1: Fred is a knave.
If Fred is a Knave, he must have told to the other natives that he wasn't, remember that Knaves will never tell the truth. In that sense, George said that Fred denied being a knave, he would be telling the truth (Fred is a knight) and Quincy said that Fred is a knave, which would also be true (Quincy is a knight too).
-SCENARIO 2: Fred is a knight
If Fred is a knight, he must have told to the other natives that he wasn't a knave, he would be telling the truth. In this case, George would also be telling the truth by ensuring that Fred denied being a knave (Fred is a knight). However, Quincy would be lying to ensure that Fred is a knave. In this scenario Quincy is the knave
In conclusion, in both scenarios, there is only one knave.