Edit: it appears that this is not exclusive to ADHD.
Posting this meme stemmed from my own efforts to explain my thought process when doing math and how it is similar to other people with ADHD doing math, while being different from every neurotypical person I'd talked to on the same subject.
While I didn't make the meme itself, instead finding it in my saves and wanting to share, I did accidentally spread misinformation that I had only backed up with personal anecdotal evidence.
I'll leave this up just so people can see the explanation below but this appears to not be ADHD related and just due to different people doing math in their heads differently...
Nah, I'm down with the 9s. 9+6 is 15 so it must be 13
Nah that's 8+8=16 so 16 -2 is 14. 14 -1 is 13, so 13. or as my maths teacher said. Wat? 1 point, negative 0.5 for incorrect formula 0.5 total. Even though it always worked!
Edit: Hell other ways to work it out. 7+7=13 logically vs my calculator so 5+5+5 = 15. 15 is incorrect why? because +5 is +2 more than necessary so 7+7 must equal 5+5+3 which = 13 or as my mental maths exam told me Fuck you! You Fail! Can't do maths in 10 seconds then you are either retarded or have another mental issue, to the stupid class you go! (It wasn't stupid class if those students got the support they needed they would have excelled!) (You had to pretend to be "normal" to make "academic progress"))
3+3 =6. 6 < 7 so 3+3+3+3 = 12 but 6<7 so 12+0.5+0.5 =13