This type of puzzle is based on a hidden pattern, not just simple addition. Let’s break it down step by step to understand how we get to the answer:

1. 1 + 4 = 5
   This one is straightforward, so we take it as is.
2. 2 + 5 = 12
   To get 12: Add 2 + 5, which equals 7, then add the previous result (5).
   So, 7 + 5 = 12.
3. 3 + 6 = 21
   To get 21: Add 3 + 6, which equals 9, then add the previous result (12).
   So, 9 + 12 = 21.

Now, for 5 + 8 = ?

4. Add 5 + 8, which equals 13. Then add the previous result (21).
   So, 13 + 21 = 34.

Thus, the answer is 34.