I wouldn't really be able to actually watch something and chat and do math problems. It would be more like 20 minutes of each at a time.
Maybe another way to say it is that in high school math problems fit into a small enough chunk of memory that you could store it to disk and load it back into working memory in a few minutes.
On the other hand, I literally can't fit my current work project into working memory. It's just too big. I have to page it to stored notes. At the end of the day, I write to myself where I need to pick up the next day, and then the next day I spend 20 minutes following my notes to load that context back into working memory.
I don't think I'm bad at this stuff either, because my solo side projects don't have this problem. I can pick those up for an hour at a time and it's fine. But my work projects...