Which number should replace the question mark?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

There was a man he lives in a hotel each morning he presses the first floor button each evening if there is a person in the elevator he asks him to press the 10 floor button if there is no one in the elevator he takes the stairs why.

What do you call a fish without an eye?

What is the fastest way to double your money?

Find the next number in the sequence

1, 2, 6, 21, 88, __?

P is the father of Q and S is the son of R. T is the brother of P and has a daughter U. If R is the sister of P, then what is the relation between U, Q and S?

Can you decipher the two rows to find the hidden word?

Two in a corner, one in a room, zero in a house, but one in a shelter. What is it?

From a pack of 52 cards, I placed 4 cards on the table.

I will give you 4 clues about the cards:

Clue 1: Card on left cannot be greater than the card on the right.
Clue 2: Difference between the 1st card and 3rd card is 8.
Clue 3: There is no card of an ace.
Clue 4: There are no face cards (queen, king, jacks).
Clue 5: Difference between the 2nd card and 4th card is 7.

Identify four cards?