I'm thinking of having my PCs meet a Givin at some point in their travels. I did some reading and found that Givin in polite society greet each other with math problems. How would you describe this narratively?

I was thinking about making my PCs do Hard Knowledge (Education) checks to see if they could solve it

I was thinking about making my PCs do Hard Knowledge (Education) checks to see if they could solve it

That sounds reasonable to me. Just do some google searches on some difficult and fancy sounding calculus problems (and their answers), then have the players roll to see if their characters know it.

I'm thinking of having my PCs meet a Givin at some point in their travels. I did some reading and found that Givin in polite society greet each other with math problems. How would you describe this narratively?

Not sure if I would. Unless one of your players plays a Givin as well, there's no reason why a wandering Givin would expect some alien to "speak in math" the way they do. Givin aren't exactly primitive recluses who don't know how the rest of the galaxy interact with others.

I was thinking about making my PCs do Hard Knowledge (Education) checks to see if they could solve it

Sure, that would work mechanically. But what would be the consequence of succeeding or failing? And what would Advantage and Threat mean? If you really want to impress the strangeness of Givin society on your players it might be better to have them, in the natural course of an adventure, come across some communication between two Givin that is based on math. The Education check would then represent how much/accurate information the players picked up.

I'm not familiar with Givins, but I think having a knowledge check would be a decent way to go about it.

Advantage and threat could be resolved the way they might for a Charm check. If the PC passes the knowledge check, the Givin might be impressed with them. If they fail with Advantages, the Givin might not trust the PC but might have positive feelings toward them.

If the PC passed with Threat, the Givin might trust them initially but have reservations based on the flubbing of the syntax in the explanation or something.

Knowledge: Education or Xenology would be appropriate. I'd make the Xenology check slightly harder. That said, this would just be to perform a formal greeting/reply, which, if successful, might grant <B> on a future social check, or <S> on a failure. It is a good bit of flavor though.

Back in the day when I was doing Fandom Comics clone wars fan sourcebook material for D20/Saga, I did stats and a write up for the Givin Wavecrest-Frigate. All the measurements/stats/numbers were prime numbers or pi or a fibronachi sequence or something. Givin are a lot of fun.