Can you spot what's wrong with the following sentence?

PETER WAS ANGRY AT
HIMSELF BECAUSE HE
ACCIDENTALLY LEFT THE
THE KEYS TO HIS CAR
AT HIS FRIEND'S HOUSE.

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

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.

You are given with the following sum. Each of the letters can be decoded as a digit. If we tell you that D = 5, then can you solve it entirely?

DONALD
+GERALD
=ROBERT

Rectify the following equality 101 - 102 = 1 by moving just one digit.

A plane crashed between the border of Mexico and America. Where do you bury the survivors?

what does this picture(rebus) riddle means ?

Write the next letter in this sequence.
O, T, T, F, F, S, S, E, __
**Hint: It is a Number Series Puzzle

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

Can you make a fire with just a single stick?