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 = ?

How can one talk without saying a single word?

The person who makes it has no need for it; the person who buys it has no use for it. The person who uses it can neither see nor feel it. What is it?

If we tell you that there is a relation between the numbers and letters in the given figure, can you analyze it and find the missing letter in the last box?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

Two friends were betting. One said to the other, "The coin will be flipped twenty times and each time the coin lands on the head, I will give you $2 and each time it lands on the tale, you will give me $3." After flipping the coin twenty times not a single penny was exchanged among them.

How many times did the coin land on heads?

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Who always enjoys poor health?