Can you find the odd number in the following?

2716, 4135, 5321 and 7145

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

Replace the question mark with the number below given a simple math problem.

Prove that the below maths equation is true.

8 + 8 = 91

Can you count the number of triangles in the given figure?

Using Only Five 5's and any mathematical operator make sum as 37

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

Replace the question mark in the picture below.

A swan sits at the center of a perfectly circular lake. At an edge of the lake stands a ravenous monster waiting to devour the swan. The monster can not enter the water, but it will run around the circumference of the lake to try to catch the swan as soon as it reaches the shore. The monster moves at 4 times the speed of the swan, and it will always move in the direction along the shore that brings it closer to the swan the quickest. Both the swan and the the monster can change directions in an instant.
The swan knows that if it can reach the lake's shore without the monster right on top of it, it can instantly escape into the surrounding forest.

How can the swan successfully escape?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?