Answer: Both Alex and Carl are wearing hats.

Reason:
As per given information we understand that, Bob is not wearing a Hat, Carl is wearing a hat.
Now if Alex doesn’t wear a Hat, than Bob must wear a Hat.
But he is not wearing a Hat. So it implies Alex is also wearing a Hat.
So Alex and Carl are wearing hats.

Correct answer : 8

Method-1
√9+√64=11
√4+√25=7
√1+√49= 8?

Method-2
Addition of two larger numbers minus the smaller number
(9+6)-4=11
(4+5)-2= 7
(4+9)-1= 12?

The answer to this “Missing Number in Last Triangle Puzzle“, can be explained with smart solution. Addition of two larger numbers minus the smaller number of the Triangle.