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

An octopus has 8 legs. A hippogriff has 6 legs and 2 pairs of wings. A sphinx has 6 legs and one pair of wings. Now we have all 3 kinds and a total of 18 insects in a cage. We have a total of 118 legs and 20 pairs of wings. How many insects do we have of each kind?

Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()

How many triangles are there on the puzzle below?

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.

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

Replace each alphabet with the number (1-9) to make the below equation correct.

AB * C = DE - F = GH / I

Find out the missing number in the picture attached:

Using Only Five 5's and any mathematical operator make sum as 37

I am a prime number.
The double of myself is equal to the square of me.

which number am I?