If there are fifteen crows on a fence and the farmer shoots a third of them, how many crows are left?

Using the clues below, what four numbers am I thinking of?

The sum of all the numbers is 31.
One number is odd.
The highest number minus the lowest number is 7.
If you subtract the middle two numbers, it equals two.
There are no duplicate numbers.

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.

In Greek mythology, the Sphinx sat outside of Thebes and asked this riddle of all travellers who passed by. If the traveller failed to solve the riddle, then the Sphinx killed him/her. And if the traveller answered the riddle correctly, then the Sphinx would destroy herself. The riddle:

What goes on four legs in the morning, on two legs at noon, and on three legs in the evening?

Oedipus solved the riddle, and the Sphinx destroyed herself.

Can you fill the blank with the correct number?

6 30 870 756030 _____

What is the next number in the series?

15 29 56 108 208 ?

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

I am a type of room you cannot enter or leave. Raised from the ground below, I could be poisonous or a delicious treat. What am I?

I have a clock(12-hour format) and both the needles of the clock overlap at 12:00.
After how much time, they will overlap again?

Find the next number in the series

12, 20, 40, 72, 116, 172 ?