Replace the question mark with the correct number below.

You need to move three matchsticks to form three squares. Can you do it?

Can you find the ages of a son, father and grandfather based on the following facts?
The sum of the ages of grandfather, father and son is 140 years.
The age of the son in months is the same as the grandfather in years.
The age of the son in days is the same as the father in weeks.

Find out a multi-digit number that if multiplied by the number 9 or any of its multiplications products (i.e. 18, 27, 36, 45,..) will result in the multiplication factor repeated (n) number of times.

In a chess board, the queen piece can move horizontally, vertically and diagonally freely. The picture represents the same.Can you place 8 queens on the board in a manner that none of the queens can attack each other?

If eleven plus two equals one, what does nine plus five equal?

Why is Saturday stronger than Monday?

There's one "sport" in which neither the spectators nor the participants know the score or the leader until the contest ends.

What is it?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

Can you complete the sequence?

192, 021, 222, 324, 252, 627, 2__, 9__?