What is full of holes but still holds water?

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

Solve the following series:
AZ, GT, MN, __, YB

People put me on the table and cut me but do not eat me. What am I?

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 replace the question mark with the correct number?

There were three women in all the swimming costumes!
One was happy and the other two were sad!
The happy one was crying and the sad ones were smiling.
Why was this?

What is always in front of you but can’t be seen?

Can you count the number of triangles in the picture below?

Can you decipher these quotes by Albert Einstein?
Blf xzm mvevi hloev z kilyovn lm gsv ovevo lm dsrxs rg dzh xivzgvw.