Can you solve the below tricky visual equation?

using four eights (8) and a one (1) and one mathematical symbol , create the number 100

Count The number of F's in the paragraph below:

"FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS"

On a charity event in Russia, Murray beat Djokovic by winning six games and losing three games.
Note: There is a total of 5 service breaks(one who serve lost the game).
Who served first, Djokovic or Murray?

There's a day, that comes around once a year.
To celebrate the man, you hold dear.
He gave you life, love and will pick you up if you fall.
When it comes to guys like him, He's the best of all.
Who is he?

Make the seating arrangement of 10 children in such a way that there are 5 rows with 4 children in each row.

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

Take 9 from 6, 10 from 9, 50 from 40, and leave 6.

How Come ??

Complete the table series riddle by finding the number that can replace "??".

I organized a small get together at my home.
In the party , i have a barrel with some whiskey in it.

Suddenly Guest 1 say 'I bet this barrel of whiskey is more than half full'.
'No, it's less than half full' Guest 2 replied.

I don't have any measuring instrument and without removing whiskey from it , how can i determine which of the guest is right ?