Can you convert the number zero(0) into a positive number using just one mathematical operator ?

What does does this rebus picture means ?

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?

Solve the equation in the image by looking at the pattern closely.

Replace the question mark in the picture below.

When can we add 2 to 11 and get 1 as the correct answer?

What does this rebus puzzle means ?

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?

Take one out and scratch my head, I am now black but once was red. What am I?

You are playing a game with your friend Jack. There are digits from 1 to 9. You both will take turn erasing one digit and adding it to your score. The first one to score 15 points will win the game.

Would you want to play first or second?

PS: The sum should be exactly 15.