What do you answer even though it never asks you questions?

Why is 6 afraid of 7?

Can you find out which options fits best with the missing column?

Can you fill the blank with the correct number?

6 30 870 756030 _____

How can a man go eight days without sleep?

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.

What is next number in the pattern below:

131 517 192 123 ?

A boy purchased a book from a bookkeeper and gave him $100.
The cost of the book is $50 but the bookkeeper has no change, so he gets the change from the next shop and returns the boy his $50.

After some time the next shopkeeper came with the $100 note and told the bookkeeper that the note was a fraud, so he took the money back.

How much loss did the bookkeeper face?

The first person saw the bridge step on it and crossed,
the second person saw the bridge did not step on it but crossed,
the third person did not see the bridge did not step on it but crossed.
Who are these people?

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?