Can you replace the question mark with the correct number in the below table sequence?

Find the missing number in the sequence below:

I am five letter word that is under you.
If you remove my 1st letter, then I am over you.
If you remove my 1st and 2nd letters then I am all around you.

Who am I?

Can you replace the X (both small and big x) with the numbers between 1 to 19 such that all the rows of 3 numbers between X (big x) sum to 23?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

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

Can you find the number?

How many triangles can you find in this given picture?

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different.

How do you measure 45 minutes?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

Three logicians went to bar for having a drink. The bar person asks the logicians "Do they all want to have the drink?". The first logician replied, " I don't know". The second logician replied, " I don't know". What is the reply of the last logician?