Can you replace the question mark with the correct number?

why number 8549176320 is one of a kind?

A woman is sitting in her hotel room and hears a knock at the door. She opens the door to see a man whom she’s never met before. He says, “I’m sorry, I have made a mistake, I thought this was my room.” He then goes down the corridor and into the elevator. The woman goes back into her room and calls security. What made the woman so suspicious of the man?

The below given figure comprises of a pattern through which you can determine the missing letter. Can you push your mind to find the pattern and add the missing letter?

Can you count the number of quadrilaterals in the picture below?

Solve the following series:
AZ, GT, MN, __, YB

I am lying and I always lie. Tell me whether I am lying or telling the truth.

You are an expert on paranormal activity and have been hired to locate a spirit haunting an old resort hotel. Strong signs indicate that the spirit lies behind one of four doors. The inscriptions on each door read as follows:

Door A: It's behind B or C
Door B: Its behind A or D
Door C: It's in here
Door D: It's not in here

Your psychic powers have told you three of the inscriptions are false, and one is true. Behind which door will you find the spirit?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

What number divided by 4 is the same as that number minus 4?