I have teeth but i don't bite. Who Am I ?

What do you get if you add 2 to 100 four times?

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 ?

Can you move 2 matchsticks to form four equal sized squares.

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

John was piloting a plane behind a car but was never able to overtake it. Why?

A chicken farmer has figured out that a hen and a half can lay an egg and a half in a day and a half. How many hens does the farmer need to produce one dozen eggs in six days?

Can you find out a way through which you can make five squares out of the given figure by moving just six match sticks?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

What jumps when it walks and sits when it stands?