On the island of Delzzup there are two types of inhabitants, knaves and knights.
Knaves always lie and knights always tell the truth.
Dave was having lunch with Darren but wasn't sure whether he was a knave or knight.
Dave decided to test Darren by asking him to ask the waiter whether he was a knave or a knight.
Darren said that the waiter had said that he was a knight.
Can you work out if Darren is a knave or a knight?
Answer: Darren is a knight.
Darren asks the waiter "Are you a knight or a knave". If the waiter is a knight he will say so, but if he is a knave he will lie and still say he is a knight. Therefore the waiter will always reply that he is a knight. As Darren correctly tells Dave that the waiter said he was a knight, we know that Darren is a knight (but we know nothing of the waiter).