Which number should replace the question mark?

I have some blue and red sock in my drawer. I have a total of 4 socks. I pick 2 socks and the chance that I get a pair of red socks is 1/2.

What is the chance of picking a pair of blue socks?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

How many words can a quill made with the feather of a pigeon write with a 100ml bottle of black ink?

A mules travels the same distance daily.
I noticed that two of his legs travels 10km and the remaining two travels 12km.
Obviously two mules legs cannot be a 2km ahead of the other 2.

The mules is perfectly normal. So how come this be true ?

I got a bee but no honey.
got an eye but am still blind.
got a sea but no water.
got a tea but no coffee.
got a why but no answer.

What Am I?

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

Rearrange the letters in "new door" to make one word.

Remove two matchsticks to make the below equation correct.