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

Can you find the odd one out from the below words ?

First Second Third Forth Fifth Sixth Seventh, Eighth Nine Ten Eleven Twelve.

Can you replace the question mark with the correct number in the below table sequence?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

Give it food and it will live; give it water and it will die.

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

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

You’ll find me on Mercury, Earth, Mars, Jupiter, Saturn, and Uranus. But never Neptune, or Venus. What am I?

There was a man he lives in a hotel each morning he presses the first floor button each evening if there is a person in the elevator he asks him to press the 10 floor button if there is no one in the elevator he takes the stairs why.

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?