Knights and knaves again on an island In an island there are 3 inhabitants, one of which is a knight (who always tells the truth) and the other two are Jokers who randomly decide whether to tell truth or lie. The 3 men have the numbers 1, 2 and 3 on their t-shirt. You need to find at least one person who can give you some information, but the problem is that you do not know who is who. You can ask use one question to one of them, which must have a number as an answer, in order to determine the knight. 
  What question will you ask?


I have never dealt with any such type of problem. 
Obviously the question must be something related to the numbers they have on their t-shirt.

Any help will be appreciated :)

(this is not homework - I wish I were 17, even if I had to bear with tons of homework!! Unfortunately I am 64!)
How about this question:


  If you have decided to tell the truth for this question, please answer with the number of the knight, and if you have decided to lie, please answer with the number of one of the jokers.


Truth tellers will respond to the first clause truthfully, giving you the number of the knight, and liars will respond to the second clause falsely, giving you the number of a someone who is not a joker. 

As far as I can tell, this is a "legal" question. The question certainly needs to refer to the joker's decision to be truthful; otherwise, the Joker's two possible states would give different answers, meaning you cannot determine the truthfulness of their answer.
Assuming even Jokers answer in the way we can consistently assign truth values to their answers, we can ask, for example,

Let $u$ be the number of Knight. Let $v$ be the number you will answer to my question with. Let $x$ be defined as
$$x = \begin{cases}
u, &amp; \text{if your answer to this question will be true}\\
v, &amp; \text{if your answer to this question will be false}
\end{cases}$$
 What is $x$?

Assume person we ask will decide to provide true answer (they are Knight or Joker who answers true). Then $x$ is number of knight. As answer is true, the answer will be $x$ - ie number of knight.

Assume person we ask will decide to provide false answer, and their answer will be $v$. Then $x = v$, and their answer will be true, not false! So they can't consistently provide false answer.

So both Knight and Joker will answer to this question with number of Knight.