Find the missing number?

Answer: Option C

Moving Left to Right:

8 + 4 = 12
12 + 3 = 15
15 + 2 = 17

Now repeat,
17 + 4 = 21
21 + 3 = 24
24 + 2 = 26.
Again,

26 + 4 = 30
Missing Number = 30.

30 + 3 = 33
33 + 2 = 25