What always comes into a house through the keyhole?

I have eight fingers and two thumbs but I do not live. What Am I?

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?

Can you replace the question mark with the correct number?

An evil man kidnapped someone and made them take one of two pills. One was harmless, but the other was poisonous. Whichever pill the victim took, the kidnapper took the other one. The victim took their pill with water and died. The kidnapper survived. How did the kidnapper get the harmless pill?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

Prove that the below maths equation is true.

8 + 8 = 91

John is asked to stand behind Jacob and Jacob is asked to stand behind John. Both of them feel confused about it and don't know what to do?

But it is quite possible, do you know how?

A brand new Mobile Phone was on sale at 20% as a promotional offer. By what per cent must the Mobile price be increased to sell it at the original price again?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M