Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

Replace the question mark with the number below given a simple math problem.

Aman has 1.15 rupees in his pocket. There are a total of 6 coins in his pocket.

When his friend asked him for a change, he could not give change for a rupee and five paisa.

Can you tell which coins he has?

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.

Two in a corner, one in a room, zero in a house, but one in a shelter. What am I?

What is the fastest way to double your money?

Joseph buys three kinds of chocolates for 100 rupees. The first one is priced at 5 rupees, second one at 3 rupees and third one at 0.5 rupees.

If he bought 100 chocolates in total, how many pieces do you think he bought each chocolate?

You are given four tennis balls and asked to arrange those balls in a manner that the distance between each one of them is exactly equal. How will you do it?

A family is trapped in a jungle. There is a bridge which can lead them to safety. But at one time, the bridge can only allow two people to pass through. Also, all of them are afraid of the dark and thus, they can't go alone.

Father takes 1 minute to cross, the mother takes 2 minutes, the son takes 4 and the daughter takes 5 minutes. While crossing the time taken will be according to the slower one. How can they all reach the other side in the minimum possible time?