1+4 =5, 2+5=12, 3+6=21 then 8+11 ...
The answer to 8 + 11 is 19
you take the 5 from the first part and add it to the 2+5. This gives you 12. Then take the 12+(3+6) and this gives you 21. 21+(8+11) and you get 40.
