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

what does this picture(rebus) riddle means ?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

In the given figure, move three matchsticks so that the resulting figure contains two rectangles.

You walk into a room and see a bed. On the bed, there are two dogs, five cats, a giraffe, six cows, and a goose. There are also three doves flying above the bed. How many legs are on the floor?

Two boys were admitted to a school. When the headmaster asks them about their parents, they tell him that they have same parents (father and mother). On further inquiry, it turns out that they both share the same date for their birthday.

"Are you twins," ask the headmaster.
"No," replies the boys.

Is it possible?

A game is being played where eight players can last for thirty-five minutes. Six substitutes alternate with each player in this game. Thus, all players are on the pitch for the same amount of time including the substitutes.

For how long is each player on the pitch?

You bought me for dinner but never eat me. What am I?