How about a fun brain teaser?

[AviatorTom]

This is an interesting puzzle from the puzzle guru Nobuyuki “Nob” Yoshigahara. Can you figure out what number should replace the question mark (orange circle)?

Answer will be given tomorrow... Saturday.

[Couretsy of Morning Brew]

Updates

+1 y

The puzzle maker says the correct answer is 12. You add the digits in the two circles that point to the number, for example: 7+2+9+9=27, so 2+1+3+6=12.

15 seems to also be a valid answer. You subtract the left circle from the right circle to get the number, for example: 99-72=27, so 36-21=15 which also works for 28-15=13.

Updates

+1 y

As @love_conquers_lust has pointed out 15 doesn't work. The bottom triplet, 21-13 is not 7.

So 12 is the only correct answer.

[JacobJordan]

initially I figured it would be 15 as all top bubbles subtracted lead to 15 until you reach the last one 21-13 is 8 not 7 meaning it can't be that. my next thought was that you combine each string and add a value from the previous but that doesn't yield any stable results. then notice if you add the digits in each bubble 13 and 21 for example 1+2+3+1 = 7. checked for remaining numbers and all add up properly. so answer should be 12

[msc545]

That was my initial answer as well.

[love_conquers_lust]

15..

[AviatorTom]

Not the answer the puzzle make says, but we all like it

[love_conquers_lust]

Nope, I agree with 12. The pattern breaks at the last triplet if we take it to be 15.

[ProbablyClueless]

I guess I can kind of understand the logic behind why the answer would be 12, but I also don't think that most people's minds would approach the problem that way. Thank you for sharing this puzzle; it's a tricky one!

When you see two numbers, like a 2 and 7, beside each other like that; a lot of people would be more inclined to think that they were looking at a 27, rather than mentally separating them as two different values.

[msc545]

I think it should be 12. That doesn't quite work but I can't get any closer than that

[msc545]

I take back what I said. 12 is the only number that works.

[msc545]

The next number in the series would be 10.

[NathanDavis]

damn... it took me way too long to figure it out, lol...

[LaFemmeFatale_1]

The answer must be 15, in my opinion

[LaFemmeFatale_1]

99 - 72 = 27
45 -27 = 18

And so on.

That seems to be the pattern.

[AviatorTom]

That's not the correct answer from the puzzle maker, but it was my answer too.

[LaFemmeFatale_1]

Hmm, let me think again

[LaFemmeFatale_1]

Figured it out! 😇

[exitseven]

The puzzle maker is wrong

[juliammm]

I would vote for 15

[juliammm]

72+27=>99
27+18=>45
18+21=>39
21+ 15 => 36
15 + 13 => 28
...

[AviatorTom]

That's not the correct answer from the puzzle maker, but it was my answer too.

[juliammm]

It works, if there is another solution, then it is a bad puzzle

[juliammm]

The second solution is 12.

[AviatorTom]

Correct, and I agree with you that both 12 and 15 are valid answers

[docster]

I'd say 15.

[Meropatrick]

14? maybe

[AviatorTom]

Close, but not correct

[exitseven]

It is 15.

[Guido]

15 is my answer.