Given
1+4 =5 and 2+5 =12 and 3+6 = 21,
We need to find 8+11=?
The given sets of addition follows a series of logical thinking
We can notice that
1+4 = 5 ———-(i) as per mathematical techniques
2+5 = 7———-(ii) as per mathematical techniques
Given 2+5=12
Here they have added the result of 1+4 = 5
So 2+5= 7 + 5 =12 ( from (i))
Similarly
3+6 =9 ——-(iii)
3+6= 9 +12= 21 ——- (from (ii)
So
8+11=19 +12 = 40 (from (iii))
Hence
1+4 =5 and 2+5 =12 and 3+6 = 21, then 8+11= 40