I saw this on the internet and managed to do all but one of them. Scam school on Youtube describes this as "the hardest puzzle ever", although I couldn't say it's anything more than a fun brain teaser any middle school student should be able to solve.

The reason I failed to do one was due to forgetting one crucial nugget of information, which I've added to the hints below. If you remember what you learnt in math class, however, you should have no trouble getting them all with no hints at all.

Also note that there are a number of solutions to most if not all expressions so the answers provided below are by no means final or complete.

So, finally - the puzzle: using only symbols that do not include any alphanumeric characters, find the missing mathematical operators that make the following expressions hold true. Hence while all basic operations from addition to division (not exclusively) are fine, squaring is illegal, as is taking the cube root, etc. That is, any common mathematical operation you can express on paper without using alphanumeric characters is fair game. You cannot modify any provided symbols (notably you cannot sidestep the problem by turning the equal sign into a not equal sign). I've provided the solution to one simple case as an example:

0 0 0 = 6
1 1 1 = 6
2 2 2 = 6
3 3 3 = 6
4 4 4 = 6
5 5 5 = 6
6+6-6 = 6
7 7 7 = 6
8 8 8 = 6
9 9 9 = 6

Here are a few hints in case you get stuck:

#1 - doesn't give away anything, but can end up saving you time

[spoiler]Leave 8 for the end[/spoiler]

#2 - another almost harmless hint

[spoiler]Do 1 before 0[/spoiler]

Have fun!

I just did:

0+0+0 <= 6

etc
9+9+9 >= 6

I don't think I was entering into the spirit properly :)

How does NOT ZERO equal ONE ?

How does NOT ZERO equal ONE ?

Mind the order. And read the solution.

For 8 I did

8 - sqrt(sqrt((8+8))

Though you were right doing 9 first helped since I remembered the existence of the square root due to not having applied it within the 5 preceding seconds :/ Writing the operators on paper would make this easier I guess?

I wonder if imaginary numbers could be applied somehow...

EDIT: also I was confused in the beginning since I thought I could only have 1 mathematical operator in each of the 2 spaces, like in the example

I'll confess that I read the solutions--those given for 0 and 1 are rather clever!

My own approach was similar to C0lumbo's: I simply inserted plus-signs on the left, then changed the "equals"-symbols to "not-equals" symbols, which can be done either by a line through the "equals"-symbol, or by adding an exclamation-mark before it.

Yes, did it! :-) Was really stuck on that first one until I remembered that !0 = 1 and then it all fell into place! Wouldn't quite describe it as the "hardest puzzle ever" though. A bit like those facebook posts that say "Only for geniuses" and you're like "I'm awesome, only took me 30 seconds" :P

I feel like this needs a list of allowed operators. Square root is ok, but cube root isn't? You use 0!, which I didn't even know was a thing, but != just side steps the whole problem.

I feel like this needs a list of allowed operators. Square root is ok, but cube root isn't? You use 0!, which I didn't even know was a thing, but != just side steps the whole problem.

That would be too easy. Although I do agree that sidestepping by modifying the equality term seems like a tempting and possibly viable option if you don't know the 0! rule. I've updated the OP. IMO the toughest part is remembering that the factorial exists in the first place.

And if you re-read the description, you'll notice I was careful to word it in such a way that one would be mentioned as illegal and the other one would not.

I wonder if imaginary numbers could be applied somehow...

That was my initial thought when I first tackled 1 and 0. Would be cool if someone found a way :)

EDIT: also I was confused in the beginning since I thought I could only have 1 mathematical operator in each of the 2 spaces, like in the example

Clarified the description by showing how to do 6 first.

Didn't solve 4,8 and 9. For my defense, I thought the square root was forbidden, so I already failed at reading the riddle carefully

How does NOT ZERO equal ONE ?

And it is not the logical operation !0=1 , it is the factorial 0!=1