Can you replace the question mark with the correct number?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

In the Chess Board picture below white army is arranged. You need to add a black army on the board such that no piece is under any threat.
Note: Army comprised of 1 king, 1 queen, 2 rooks, 2 bishops, 2 knights, and 8 pawns.

If an electric train is travelling south, then which way is the smoke going?

On a magical land of Mexico , all the animal in the land are rational.

There are 10 tigers and one goat.
Tiger can eat goat but since it's a magical land , the tiger who eats the goat , turns into goat and then can be eaten by the remaining tiger(s).

If we leave them for some time then how many goat and tiger will be there , when we come back ?

A red house is made out of red bricks. A yellow house is made out of yellow bricks. And, a blue house is made out of blue bricks. So, what is a greenhouse made of?

What does the below rebus riddle means?

James ordered a fishing rod, priced at $3.56. Unfortunately, James is an Eskimo who lives in a very remote part of Greenland and the import rules forbid any package longer than 4 feet to be imported. The fishing rod was 4 feet and 1 inch, just a little too long, so how can the fishing rod be mailed to James without breaking the rules? Ideally James would like the fishing rod to arrive in one piece!

A doctor and a boy were fishing. The boy was the doctor’s son, but the doctor was not the boy’s father. Who was the doctor?

Can you find out what is missing?

1 3 5
2 4 ?

Hint: It's not six. Think out of the box.