Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

It's a 7-letter word.
If we remove 1 letter from it, it remains the same.
If we remove 2 letters from it, it remains the same.
If we remove 3 letters from it, it remains the same.
If we remove all the letters from it, still it remains the same.
What is it?

A new clothing store has a unique method of pricing items. A vest costs $20, a tie costs $15, a blouse costs $30, and underwear costs $45. How much would pants cost?

How can a man go eight days without sleep?

What does the below mathematical rebus mean?

You are an expert on paranormal activity and have been hired to locate a spirit haunting an old resort hotel. Strong signs indicate that the spirit lies behind one of four doors. The inscriptions on each door read as follows:

Door A: It's behind B or C
Door B: Its behind A or D
Door C: It's in here
Door D: It's not in here

Your psychic powers have told you three of the inscriptions are false, and one is true. Behind which door will you find the spirit?

Irene killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

What is always in front of you but can’t be seen?

Can you name some countries which do not have the alphabet 'A' in them?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?