Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

What am I?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

Count the number of triangles in the picture below:

Can you place six X (crosses) in below board without making three in a row in any way ?

John is now two fifth of his older brother's age and two years from now he will be half of his older brother's age.
Two years ago, John was only one-fourth the age of his older brother age at that time.

How old is John now?

Whats the next number in the below number sequence pattern.

The husband and wife were jogging in the morning. To match every two steps of the husband, the wife required three steps. If Both of them start with the here right foot. After how many steps do their left foot be together?

What has many teeth, but cannot bite?

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