Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

A boy and his father are caught in a traffic accident, and the father dies. Immediately the boy is rushed to a hospital, suffering from injuries. But the attending surgeon at the hospital, upon seeing the boy, says 'I cannot operate. This boy is my son.' How is this situation explained?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

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

I never was there, I am always to be.
You have never ever seen me, not ever you will.
Yet I am the confidence of everyone.

Who Am I?

Here is a conversation between a couple who both are software professionals.

Husband: Hey! What is your date of birth?
Wife Replied Angrily: It is 591062400
Husband after doing some calculations replied, "Got It".

What is the DOB of the wife?

First, think of the colour of clouds. Next think the colour of snow. Last, think of the colour of the moon. Now, what do cows drink?

It is a nine-letter word.
The exact opposite of the phrase "friendly and outgoing"
It contains the word "over".
It starts will a vowel.

What is it?

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

Can anyone tell me a word in the English dictionary which has a silent 'z'?