Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

In a mathematical quiz, you are asked the following question:

Use three 9s in a mathematical expression without dividing or multiplying to form the number one.

Can you answer the question?

What kind of band never plays music?

If all Goats are Sheep and all Sheep are Deers, are all Deers Goats ?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

There is so small cabin inside a deep forest.
All the forest burned out to worst possible but the inside of the cabin is still the same.
However all the person inside the cabin die.

How come ?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

Can you name an animal whose killing cannot be performed without spilling your own blood?

What does the below rebus riddle means?

Can you find the next number in the below sequence
3 , 7 , 10 , 11 , 12 , 17 ?