Replace the question mark with the number below given a simple math problem.

Can you find out the missing number in the grid?

Pronounced as 1 letter, And written with 3, 2 letters there are, and 2 only in me. I’m double, I’m single, I’m black blue and grey, I’m read from both ends, and the same either way. What am I?

In an interview, a boy was asked an unusual question 'How two persons sitting with a table in between them can't see each other?' He was unable to reply. Can you?

Before Mount Everest was discovered, what was the highest mountain in the world?

Can you find the key in the picture below?

There are two words one resembles the "state of rest" and the other is related to "writing/reading material".

Can you name these two words which also sound similar?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

What seven-letter word has hundreds of letters in it?

Find three numbers such that

* When we multiply three numbers, we will get the prime numbers.
* The difference between the second and the first number is equal to the third and second.