Find the missing number?

Answer: Option A

Logic:

Add up numbers in corresponding segments of each square.
The sum of the digits in the left hand segments = 20,
The sum of the upper segments = 22,
The right hand segments = 24
The lower segments = 26.

Thus,
13 + 2 + 7 + x = 26.
x = 26 - 22 = 4.
Missing Element = 4.