Cid brushed off her question, not caring if it was rude. But it was not a subject that he wanted brought up right now. Not now and probably not ever.
He quickly corrected her, saying "Not very hard. Muy es very. But, not so difficult or hard for a seventh year. Pero es but, una conjunción, si." As he had been explaining, he remembered explaining the same words to her in the past. Cid knew that she was not stupid, and had no doubt in his mind as to her intelligence. He did not think she was as smart as he was, but no one really was. He wasn't going to hold that against her.
"You know these words, but are making mistakes." He quickly repeated himself in Spanish. "Usted está haciendo errores tontos." [You are making silly mistakes.] Cocking his head to the side and tapping his lower lip in thought, he finally asked, "¿Hay algo mal?" [Is something wrong?]. He would have asked in English, but he wanted himself perfectly understood.