Can you write down eight eights so that they add up to one thousand?

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?

What does the following represent?

N N N N N N N

A A A A A A A

C C C C C C C

I came first on earth but second on the heaven.
I also came twice in a week but found just once in a year.
I stay away from months but you can find me in February.

What am I?

A man has a barrel filled with oil that weighs 100 pounds, and then he puts something into it. Now the barrel weighs less than 100 pounds. What did he put in the barrel?

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

I am the first thing you need while camping.
I am always with the person named Marcos Valencia and Carrick.
But Pogba Zlatan and Rooney think I am wasteful and do not need me.
I am the second to the last thing to add when you are making a patch.

What am I?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

Can you find the thief by just looking at the picture below?