If 21x = 79x, what is the value of x?

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?

The current time can be represented by below textual rebus.

0
=========
B.Sc
LLB

Can you tell us the current time?

When you say goodbye, I am what you need to tie.
I come as a couple and go wherever you run.
Who am I?

In case you were starting to feel confident, this one was meant for third graders in Vietnam. The answer is 66, but we don't blame you for scratching your head about how they got there.

The first person saw the bridge step on it and crossed,
the second person saw the bridge did not step on it but crossed,
the third person did not see the bridge did not step on it but crossed.
Who are these people?

Can you find the mistake in the below statement?

Can you make four (4) nines (9) equal 100?

It was a dark stormy night and a couple were in a car driving madly to a city. The car broke down and the husband had to go get help from someone who spoke his language. He was afraid to leave his wife alone in the car so he locked the car before leaving. When he came back, the car was in the same state as he had left it but his wife was dead, there was blood on the floor and there was a stranger in the car. What happened?

Three fair coins are tossed in the air and they land with heads up. Can you calculate the chances that when they are tossed again, two coins will again land with heads up?