It doesn't surprise me that after not playing for a decade you can't remember the pieces you learned. I took a couple years of lessons and kept playing for year

It doesn't surprise me that after not playing for a decade you can't remember the pieces you learned. I took a couple years of lessons and kept playing for years afterwards, and now I'd never make it far into Invention #1 from the Well-Tempered Clavier without the sheet music. I doubt much of the math you're talking about was drilled into you in elementary school and rarely used since. As a teenager and adult I'll do most of that sort of thing in my head (not long division, normally); I didn't bother as a younger kid, but it's kept coming up enough to be worthwhile, for me; I wouldn't expect so for most people in today's society, which is sort of a disappointing fact about society, but one that matters if you think of people as free agents.