[Locutus of Borg]

Does anyone know what should go in the circle with the ? in it?

I thought ti would be 15, and that would fit if the right most number was 8 instead of 7. It might be a typo, but if it isn't; can any of you figure it out?

[Blue Lion]

It's 15

[Locutus of Borg]

Could you explain your thinking? I thought it was 15, but 21 - 13 =/= 7

[BloodEagle]

Where did you find this?

It certainly looks like a typo, as I can't see any other pattern.

::EDIT::

By the way, whoever designed the layout for that image should suffer.



The drastic changes seem to indicate that there isn't an infinite pattern, or if there is, then there isn't enough information available to make it easily recognizable. I'm guessing that either the 21 was supposed to be a 20 or the 7 was supposed to be an 8.

[Enigmatic Entity]

It's 15. Note how there are two lines going to the left of each bottom circle. Minus the bottom line number from the top and you get the number in the vacant circle.

Which implies that the right most number is 8, like others have said.

[Locutus of Borg]

But we're given that the right-most number is 7

So we're all going with typo then?

[Uchuujinsan]

The answer is

Spoiler:

12

not 15

Spoiler:

9+9  + 7+2 = 27
2+7  + 4+5 = 18
1+8  + 3+9 = 21
2+1  + 3+6 = 12
1+2  + 2+8 = 13
1+3  + 2+1 = 7

Note that the first numbers are always dividable by 3, and only when it is no longer (the 28) the pattern gets "changed"

[edit]
Added spoiler tags

[BloodEagle]

 

I hate it when they cheat. 

[Locutus of Borg]

The answer is

Spoiler:

12

not 15

Spoiler:

9+9  + 7+2 = 27
2+7  + 4+5 = 18
1+8  + 3+9 = 21
2+1  + 3+6 = 12
1+2  + 2+8 = 13
1+3  + 2+1 = 7

Note that the first numbers are always dividable by 3, and only when it is no longer (the 28) the pattern gets "changed"

[edit]
Added spoiler tags

You're awesome