I think these were the missing terms in this thread:

Necessary vs. sufficient

Understanding vs. doing.

I think Cato does understand algebra, even if he couldn’t sit down at a formal problem and do one.

If someone really can’t do algebra, they really will spend their whole life getting ripped off and making bad decisions when it comes to financial transactions, etc.

So, simply by rote memory if nothing else, most people learn algebra defensively. Even if not formally.