Step-by-step Solution:

Pattern Analysis

The pattern for this puzzle is that for each circle, the sum of the two top numbers is equal to the sum of the two bottom numbers.

We can apply this rule to the final circle to find the missing number.

• 
  Top Numbers: The numbers at the top are 2 and 4.
  
  Their sum is 2 + 4 = 6.
  


• 
  Bottom Numbers: The numbers at the bottom are 3 and the missing number (let's call it 'x').
  
  Their sum must also be 6.
  


• 
  Calculation: The equation is 3 + x = 6. Solving for 'x' gives us 6 - 3 = 3.
  

The missing number is 3.