What brings you down but never up?

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

All of Jacob's shoes are red except two.
All of Jacob's shoes are green except two.
All of Jacob's shoes are yellow except two.

How many shoes does Jacob have?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

Can you find a seven digit number which describes itself. The first digit is the number of zeros in the number. The second digit is the number of ones in the number, etc. For example, in the number 21200, there are 2 zeros, 1 one, 2 twos, 0 threes and 0 fours.

A king sentenced a man to the death sentence for some crime he had committed. Known for his kindness, the king told the culprit that he had a choice to die in a way he decides.

The culprit was clever and said something that saved him from death. What method do you think he must have chosen for his death?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

What Does this text mean:

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