How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

It is deaf, Dumb and Blind!!!

Still, always tells the truth. What is it?

Jim and Sarah are in a long-distance relationship. Jim buys an engagement ring for Sarah and wants to mail it to her. Unfortunately, the only way to ensure the ring will be received is to place a lock on the package. Jim has locks and Sarah has locks, but neither has keys for each other’s locks. How can they make sure the ring isn’t stolen?

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10

Can you place six matchsticks in a manner that each of the matchsticks is in touch with the other five matchsticks?

I make two people out of one. What am I?

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?