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

There was a minor accident with a doctor's son but the doctor noticed no major injury. After the treatment, the father of that doctors son is sitting with the son of the doctor without the doctor being in the room.

How can this be possible?

Three cars are driving on a track that forms a perfect circle and is wide enough that multiple cars can pass anytime. The car that is leading in the race right now is driving at 55 MPH and the car that is trailing at the last is going at 45 MPH. The car that is in the middle is somewhere between these two speeds.
Right now, you can assume that there is a distance of x miles between the leading car and the middle car and x miles between the middle car and the last car and also, x is not equal to 0 or 1.
The cars maintain their speed till the leading car catches up with the last car and then every car stops. In this scenario, do you think of any point when the distance between any two pairs will again be x miles i.e. the pairs will be x distance apart at the same time ?

It spends most of its day eating white, but when it’s quick enough, it gets to eat fruit and sometimes some blue things. It’s in a dark room, where the walls are blue, it runs from a ghost that roams the halls and haunts it all the time. What is it?

Which alphabet letter is a question?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

There are nine letters in the below-given diagram. You have to form a nine-letter word using these letters.

The measurement of time, That can't be found on a clock, But can be looked upon on a map.

Who is He ?

Prove that twice of ten is the same as twice of eleven.

It is raining today at 11:59 am. What is the probability of sunny weather after 72 hours?