Question

1+4=5 2+5=12 3+6=21 8+11=

Answer 1

Alright, so here's what's happening.

The first equation set a standard.

After that, the numbers being summed are actually added to the answer of the previous Equation.

So 8+11 will be 19 and 19+21 = 40

Answer

8+11 = 40

Answer 2

The correct way to write it would be
1+4=5
5+2=7
7+5=12
12+3=15
15+6=21
21+8= 29
29+11= 40
So your final answer is 40
Hope this helped!