What does does this rebus picture means ?

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

Can you solve the below algebraic mathematical equation?

(J+O+I+N+T)3 = JOINT

A man is found dead with a knife in his back When the investigation is done. A chair lays beside him and the forensic team finds moisture around the body.

If he committed suicide, how did he do it?

Count the number of balls in picture below:

What is more useful when it is broken?

Spot 5 differences in two Christmas tree below:

No one wants to have it, but if one got it, he does not want to lose it. What is It?

It's pretty hard to give up.
If you remove a part of it, you will be left with a bit.
Even if you remove another part, the bit still remains.
Remove one more and it still remains.

What is it?

Three people enter a room and have a green or blue hat placed on their heads. They cannot see their own hat but can see the other hats.
The colour of each hat is purely random. They could all be green, blue, or any combination of green and blue.
They need to guess their own hat colour by writing it on a piece of paper, or they can write 'pass'.
They cannot communicate with each other in any way once the game starts. But they can have a strategy meeting before the game.
If at least one of them guesses correctly they win $10,000 each, but if anyone guesses incorrectly they all get nothing.
What is the best strategy?