Which number should replace the question mark?

Replace the question mark in the picture below.

I am not a bull but I have horns.
I am not an ass but I have a pack saddle.
Wherever I go, I leave silver behind me.

Who am I?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

With the help clues provided in the image, can you find the 5 digit key?

I am a number I am not an odd number I am higher than 90 I am not higher than 100 If you subtract me from 100, you get nothing. What number am I?

Which city is three-fifths chick two third cat and 50% goat?

You are stuck on an island where you have nothing. You find four pieces of paper somewhere on the island. What will be your strategy to escape from the island safely?

PS: No other resource is available to you on the island, neither can you build anything.

I have an eye but still cannot see.

Who am I?

A man who was outside in the rain without an umbrella or hat didn’t get a single hair on his head wet. Why?