Mom was a good teacher, but do Auggie and his mother agree that she it terrible at?

Auggie and his mother both agree that she is terrible at fractions.

I just think you need to learn more than I can teach you," Mom said. "I mean, come on, Auggie, you know how bad I am at fractions!"

"Let's just talk about it later," said Mom. I could tell she and Dad were going to get in a fight about it. I wanted Dad to win the fight. Though a part of me knew Mom was right. And the truth is, she really was terrible at fractions.