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

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

I have a head like a cat and feet like a cat, but I am not a cat. What am I?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

One night, a man runs away from home. He turns left and keeps running. After some time he turns left again and keeps running. Later, he turns left one more time and runs back home—but when he gets home, he finds a man in a mask. Who was the man in the mask?

How many bananas can you eat if your stomach is empty?

If in a car race, the man who came two places in front of the last man finished one ahead of the man who came fifth, how many contestants were there?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

I am 5 letters long.
My first two tell you who I am
My first 3 could be a medicine
My last three reversed could be a young boy.
My 4th, 3rd and 2nd in that order could be a fruit drink.
If you have me you may hang me round your neck
WHAT AM I ?

I live in a bowl. I can swim. I have a tail. I also have fins and big eyes. What am I?