What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

In the following series, a set of numbers is progressing with a particular pattern. Can you deduce that pattern and find the missing set?

(2 + 6), (21 + 6), (58 + 6), (119 + 6), ___

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

I have four wings but can't fly.
I express no emotions.
I am found on the exact spot every time you look.
I keep toiling away with a little sound.

Do you know what am I?

Can you decipher the below rebus?

PBLUESAISNUERSES

Analyze and find the missing item in the sequence:
16, 06, 68, 88, __, 98

A bus driver was heading down a street in Mexico. He went right past a stop sign without stopping, he turned left where there was a "no left turn" sign, and he went the wrong way on a one-way street. Then he went on the left side of the road past a cop car. Still - he didn't break any traffic laws. Why not?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

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