Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

Thirty friends were on a hiking trip when they decided to enjoy the bonfire. They assembled for it and agreed to play a game. For that, they divided themselves into five teams with seven members each, forming five rows.

How did they manage to achieve this formation?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

Only one colour, but not one size,
Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
What is it?

It belongs to you, but other people use it more than you do. What is it?

Four men were in a boat on the lake. The boat turns over, and all four men sink to the bottom of the lake, yet not a single man got wet! Why?

Which is faster, Heat or Cold ? Explain.

My first is in chocolate but not in ham. My second is in cake and also in jam. My third at tea time is easily found. Altogether, this is a friend who is often around. What is it?

Solve The below Equation:

ALFA + BETA + GAMA = DELTA

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?