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...
I was in school way before the new math thing. I figured out doing it all in my head like this on my own because i hated writing out and solving math problems. Especially long division, and was able to coast through all my math classes. It felt pretty natural, which is how I think they decided to start doing "new math".
9 X 47= ?
No problem.
10 X 47 is 470. Need 47 less than that.
70 minus 40 is 30.
30 minus 7 is 23.
9 X 47 = 423.