It's 3X3-3
Discussion
Go for the rest without looking at Vic's answers!
Too late…
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2+2+2=6
3X3-3=6
4+4-root4=6
5+5/5=6
6+6-6=6
7-7/7=6
Cuberoot(8)+Cuberoot(8)+Cuberoot(8)=6
I'm stuck at 9 for now
8 is correct but violates the symbols only rule on a technicality since writing out cuberoot in common written notation requires the number 3. There's another solution thoguh, see if you can find it!
8 and 9 were the two hardest ones for me! Somehow I was stuck on 4 for a while too.
It's interesting how there's actually a lot of different solutions available for most of them equations.