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It's my first time here, so I'm just chumping out a random puzzle I found interesting. It is the following:

1 + 7 = 6

2 + 6 = 4

3 + 10 = 6

5 + 2 = ?

It's probably super easy for you geniuses because I've been the level of ability here, but I just wanted to have throw something out there.

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closed as too broad by Deusovi, xnor, Mohit Jain, CodeNewbie, Jon Mark Perry Mar 21 at 8:23

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

5  
Ugh, I hate when people abuse the + and = signs. – Deusovi Mar 20 at 15:34
    
Does + mean something else here? – user230452 Mar 20 at 16:21
2  
Hello! Thanks for posting your question! Unfortunately, I'm not sure it's a good fit for this site. We prefer puzzles that have one demonstrably correct answer, especially for mathematical puzzles. But as discussed in this thread, puzzles where you're given a mystery function and have to guess one of the numbers can arguably have a large number of valid answers. This isn't to say that your puzzle is bad, just that it isn't the best fit for this particular site. – Kevin Mar 20 at 18:21
    
Oh. I'll try to give a better puzzle next time, thanks for the heads up! – MinusReputation Mar 20 at 22:50
up vote 9 down vote accepted

One possibility is

5

Because

You're spelling out the numbers, adding the number of letters, and subtracting 2.

ONESEVEN is 8 letters; 8-2=6
TWOSIX is 6 letters; 6-2=4
THREETEN is 8 letters; 8-2=6
FIVETWO is 7 letters; 7-2=5

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My guess is

7

Because

You're summing the number of vertices in each number:

[picture]

(However, as that isn't necessarily very mathematical, I don't necessarily think this is the right answer.

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This seems a viable answer, as any, to me. – Khale_Kitha Mar 20 at 17:49
    
If this answer is correct, the puzzle is rather disappointing, because this is not an equivalence relation (not symmetric). 6 only has one vertex. – Columbo Mar 20 at 22:12
    
It's not the answer, but I must admit it's pretty genius. – MinusReputation Mar 20 at 22:49

My guess is …

5

Because …

Counting the letters in the english language words for each number and subtracting two gives:
one + seven = 8 letters; 8 - 2 = 6
two + six = 6 letters; 6 - 2 = 4
three + ten = 8 letters; 8 - 2 = 6
five + two = 7 letters; 7 - 2 = 5

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Rats. @BenM ninja'd me :) – Sean D. Sollé Mar 21 at 0:31

5, because you might be adding the number of syllables in each line? = can be "equals" or "is"?

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But the first and third lines have different numbers of syllables yet are both 6. – BenM Mar 21 at 0:23
    
one plus sev en e quals = 6 syllables three plus one zer o is = 6 syllables – Jason Brockdorf Mar 21 at 0:25

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