She is sitting in the library, studying. It's her most common pastime, by hours; spending time with her sister is more enjoyable but Jaromira prefers to socialize more broadly and Katarzyna would only get in the way. This is better on net; the two of them share a room, so it isn't as though her sister's time is entirely hogged by the other girls who call this boarding school "home." Or at least "prison." Katarzyna doesn't mind it, though; the school library is excellent, and basic manners and care for the books has endeared her to the librarian to a sufficient degree to lubricate the interlibrary loans process when there's something she wants to read that they don't have.
"Oh, you mean the equation, not the acronym. Failing to do the equation left to right will in general not cause you to come to an incorrect conclusion."
"...really? I could just do whatever, uh, parentheses thing, looks easiest first?"
"If you say so!"
He tries another problem, very stepwise, easiest-looking parentheses first. This time he gets it right, though this happened sometimes even pre-tutelage and might not indicate much.
Katarzyna is still excited about it, although she tries to be low-key about her excitement.
This procedure slightly improves his error rate over the next several problems.
Katarzyna continues to explain things when she notices that he's having some kind of systemic confusion.
"You're welcome!"
She wanders off to find Isabella.
"Sorry for abandoning you for your brother but I think I really helped his understanding of math!"
"...I don't know that I would have found him intrinsically interesting if I met him first but I think he qualifies as being transitively interesting on account of being your twin."
"It's not that he would have to be a certain amount of boring, it's that I hadn't previously realized that the bar existed. I don't find my sister's friends particularly interesting, but then, she mostly has casual friends, not close ones."
"Well, most people aren't very interesting, I will grant you that."
"I really hope I can synergize powers and I just haven't met two that synergize well at the same time."
"Yeah. Maybe visit a really big hospital that might have two magicals on staff at once."
"They'll probably both be healers, which seems likely to either be excellent or redundant for synergy purposes."