If 21x = 79x, what is the value of x?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

If,

Akriti = 631
Levis = 521
Sroti = 521
Aneel = 533
Then,
Sunil =?

A father's child, a mother's child, yet no one's son.

Who am I?

John was drowned by he was not wet. How?

The following "Brain Bat" means Slow Down.
S
L
O
W

Using the same logic, can you tell us what does the following Brain Bat means ?
E
V
I
G

Before reading ahead, you must know the fact that only one of the people here is telling the truth.

A says that B is lying.
B says that C is lying.
C says both A and B are lying.

Can you find out who is speaking the truth?

Known by all without exception, Forever here, for your protection, Sometimes strong, sometimes weak, Right after the night I come - hot and chic. And while millions of miles away, I always get to you, I find my way. No life around could do without me, Can you guess what I might be?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?