Admittedly, I haven’t read all of your posts, but I have read a few and I’m excited about your adventure with unlearning. As the principal of a school that’s essentially unschooling at scale, I see students work to make the transition from traditional schooling to our lovely untraditional world. It can be tough at times to break out of that familiar mold, but definitely worth the push.
So I’m wondering about why you’re doing a math problem like this one, when algebra is so much more beautiful. Have you read “Measurement” by Paul Lockhart that connects geometry and algebra in a really cool way? As well as his “Mathematician’s Lament” that discusses the core issues with math education?
You also might try Exeter’s inquiry-based math problems.
These are all math problems where there’s joy in the puzzle of figuring it out, where the focus is on the process and less on the answer, and where the problems are based in something more sensical than buying a lot of chocolate and shipping them for so much money.
And if you want more of the applied algebra (or math, in general), any writings by Jordan Ellenberg are super fascinating to read as he dissects real world with mathematical arguments.