Which Number is the odd one out?

A) 7145
B) 2716
C) 5321
D) 4135

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

If we add four times the age of John four years from now to five times his age five years from now we get ten times his current age.

How old will John be two years from now?

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

John is 45 years older than his son Jacob. If you find similarities between their ages, both of their ages contain prime numbers as the digits. Also, John's age is the reverse of Jacob's age.

Can you find their ages?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

In a town, there are over 100 flats.
Flat-1 is named first flat.
Flat-2 is named second flat.
Flat-3 is named third flat.

A visitors 'Victor' decides to walk through all the flats, he finds all the flats except flat-62.
Victor later founds that the local of the town have given it another name.

What is the name of the Flat?

This is a classy optical illusion puzzle. What more you can find except bricks in the image below?

How many triangles can you find in this given picture?