I used to be very good at math and history. But since the accident, its hard for me to understand what my teacher is saying. What is the correct part of the brain?

The answer is auditory cortex.

Explanation:

https://en.wikipedia.org/wiki/Auditory_cortex

Here is an image of the auditory cortex.

The brain has three main parts: the cerebrum, cerebellum and brainstem. Cerebrum: is the largest part of the brain and is composed of right and left hemispheres. It performs higher functions like interpreting touch, vision and hearing, as well as speech, reasoning, emotions, learning, and fine control of movement.

Explanation:

I hope this helps but ill tell you this when i was three years old I fell out of a three story apartment on my head and for the longest time i litteraly had the shape of a foot ball for my head and i have pretty bad brain damage so i am very forgetful.

its bassicly asking u   to answer it in your own words does that