Elle brosse ses cheveux.

my teacher said this is wrong. what should it be?

In this french correct ? i dont know if the person i am talking to is a female or male im assuming that wouldn't affect it but i kind of forget . i know all adjectives agree with the nouns that they modify. métier is masculine so i use the adjective bon and bon is masculine so i use un? is that how it works je pense un bon métier pour toi est un artiste ou un architecte. i think a good job for you is an artist or an architect