not even ADHD related you're just taking a route to something more readily available in your memory. that's how brains are supposed to work.

to me the detour is -1+10. whenever i see a 9 i take 1 away from the other guy and then add 10.

9 x single digit mumber works similarly; except i take away 1 and complete that to 9 by adding a number next to it.

9x7 = ?

7-1 = 6

6+? = 9

9x7 = 63