Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

What is the next number?

77, 49, 36, 18 ?

A mother is 21 years older than her child. In exactly 6 years from now, the mother will be exactly 5 times as old as the child.
Where's the father?

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

What is the value of 1/2 of 2/3 of 3/4 of 4/5 of 5/6 of 6/7 of 7/8 of 8/9 of 9/10 of 1000?

If we tell you that there is a relation between the numbers and letters in the given figure, can you analyze it and find the missing letter in the last box?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.

How many minutes are there in Feb 2017?

Note: The shortest answer is the correct answer.

If,

A = 1

B = 2

C = 3

...

...

Z = 26.

Based on above rule, you need to find an eleven letter word whose letter sum is equal to 52.