Given that Toshino Kyoko! normally outperforms everyone (including a frustrated Ayano) on examinations, it seems that Yui must be poor test-taker as such when it comes to mathematics.
Unsurprisingly, Akarin isn't equiped to handle that kind of intense attention and got all flustered/confused as a result Ayano got flustered too of course but for completely different reasons ! That would be a fun chapter to get animated if they ever decide to make another season/OVA.