Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

Which tank will fill first?

I was speeding and ran through a stop sign, yet two traffic officers who were there do nothing about it.

why?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

The day before yesterday I was 25 and the next year I will be 28. This is true only one day in a year. What day is my birthday?

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

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?

Assume the given figure to be a delicious doughnut. Yes, now you can concentrate more on the puzzle. So you have this delicious doughnut in your refrigerator when your friends come knocking at the door. There are eight of them. Now you have to make three cuts in this doughnut so that each one of you nine people can enjoy a piece of it. Neither you nor your friends would mind the size of their piece as long as they are getting it. How will you do it?

There were two grandmothers and their two granddaughters.
There were two husbands and their two wives.
There were two fathers and their two daughters.
There were two mothers and their two sons.
There were two maidens and their two mothers.
There were two sisters and their two brothers.
Yet there are only six, who are buried here,
All are born legitimate and relationships clear.
How can this happen?

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _