Can you replace the question mark with the correct letter?

6 + 6 + 6 = N
7 + 7 + 7 = E
8 + 8 + 8 = R
0 + 0 + 0 = ?

What demands an answer, but asks no questions

John can fit six large chocolate boxes or nine small chocolate boxes into a carton. How many cartons will he require to put sixty-six chocolate boxes into?

Manish and Manoj play 5 games of chess.
Both Manish and Manoj win the exact same number of games. There is no tie at all.

How?

John was going on a jungle trip. He asked his wife to pack something to eat, something to drink and something to burn if he feels cold in the jungle. When John opens the backpack he found just one thing in the bag. What was it?

In which direction should the missing arrow point?

A wealthy man lives alone in a small cottage. Being partially handicapped he had everything delivered to his cottage. The mailman was delivering a letter one Thursday when he noticed that the front door was ajar. Through the opening he could see the man's body lying in a pool of dried blood. When a police officer arrived he surveyed the scene. On the porch were two bottles of warm milk, Monday's newspaper, a catalog, flyers, and unopened mail. The police officer suspects it was foul play. Who does he suspect and why?

What is the next number in this matchsticks series riddle?

On a certain island, people are gifted with assorted eye colours. There are a hundred green-coloured and a hundred grey-coloured pairs of eyes. On that island, there is no mirror available. Thus no one knows the eye color of their own. They could have asked each other but that is prohibited. They are not allowed to converse with each other. However, they can study and analyze other's eyes. They don't even know the statistics so it is believable to them that their eyes can be blue as well. There is a chance of freedom from the island. If anyone can guess the colour of his own eyes correctly, he will be set free and can leave the island.

On one particular day, an outsider comes to the island and announces that he has seen someone with grey colour eyes. What will happen now?

The captain of a ship is telling you an interesting story and then poses a question. He says, “I have travelled the oceans far and wide. One time, two of my sailors were standing on opposite sides of the ship. One was looking west and the other one east. And at the same time, they could see each other clearly. Can you tell me how that was possible?”