1+4=5
2+5=12
3+6=21
8+11=???
Donkey Kong
I think I saw the exact same problem on the internet yesterday lol
1+4=5, 1*4+1
2+5=12, 2*5+2
3+6=21, 3*6+3
8+11=8*11+8=96
There may be other solutions but this was the one I came up with.