Find the missing number?

Answer: Option A

Logic:
Element at the Center = Sum of even numbers - Sum of odd numbers or Sum of odd numbers - Sum of even numbers

For 1st Star
8 = (6 +2 +4) - (3 +1)
2nd Star
6 = (11 +9) - (4 +8 +2)
3rd Star
x = (5 + 5 +7) - (10 +2)
x = 5
So, required number = 5.