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

John killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

Mr Black, Mr Gray, and Mr White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr Black, who hits his shot 1/3 of the time, gets to shoot first. Mr Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. If you are Mr Black, where should you shoot first for the highest chance of survival?

Find the next number in the sequence

1, 2, 6, 21, 88, __?

There are are five things wrong with this sentence; only geniuses will be able to to spot all of the mitstakes

A man started to town with a fox, a goose, and a sack of corn. He came to a stream which he had to cross in a tiny boat. He could only take one across at a time. He could not leave the fox alone with the goose or the goose alone with the corn. How did he get them all safely over the stream?

This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?

Three brothers Jacob, John, and James live in Mexico City. The product of the ages of these brothers is 175. Jacob and John are twins. How old is James?

Find three numbers such that

* When we multiply three numbers, we will get the prime numbers.
* The difference between the second and the first number is equal to the third and second.