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

How many triangles are there on the puzzle below?

A girl was sitting in her hotel room when she heard a knock on the door. She opened the door and found that a man was standing outside.
The man said, "Oh! I am really sorry, I thought this was my room."
He then walked through the corridor to the elevator. The girl did not know the man. She closed her door and called security asking them to apprehend the man.
What made her suspicious of that man? He might have been genuinely mistaken.

Baseball bat and ball cost $100. If the bat cost $99 more than the ball, what is the cost of each?

Can you name four days which start with the letter 'T'?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

Rebus Puzzle Definition: A rebus is an illusion device that uses pictures to represent words or parts of words.
What does This Rebus Puzzle Identify?

Andrew sees a very rare bird named "Ruppell's vulture". Soon Andrew was dead. Can you explain the mystery, Mr. Sherlock?

I am the beginning of everything, the end of everywhere. I'm the beginning of eternity, the end of time and space. What am I?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?