If eleven plus two equals one, what does nine plus five equal?

A shopkeeper allows people to buy a cold drink bottle in exchange for five empty bottles. A guy had a party at home and spent 77 cold drink bottles at the party. Now he has 77 empty bottles with him.

How many bottles do you think he can buy in exchange for those 77 empty bottles?

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?

While preparing the table for dinner, wife came up with an idea to tease his mathematician husband. She asked her husband to pick nine toothpicks and make ten without breaking any toothpick.

The husband was also smart and did it within seconds. How ?

Spelt forwards I’m what you do every day, spelled backwards I’m something you hate. What am I?

If you drop me I’m sure to crack, but give me a smile and I’ll always smile back. What am I?

There was a competition where the contestants had to hold something. At the end of the event, the winner was a person who had no hands or feet. What was it that the contestants had to hold?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

You are in a land where thirty men and two women were dressed in classic black and white dresses.
They begin to fight as soon as any of them move.

Where are you?

A plane crashed between the border of Mexico and America. Where do you bury the survivors?