We are given with
1 + 4 = 5
2 + 5 = 12
3 + 6 = 21
8 + 11 = ?
The answer is 40.
1 + 4 = 5 (simply 1 plus 4)
2 + 5 = 12 (this is supposed to be 7 but adding 5 from the previous sum results to 12)
3 + 6 = 21 (this is supposed to be 9 but adding 12 gives 21)
8 + 11 = 40 (this is supposed to be 19 and adding 21 gives 40)
