Which sentence is written in a formal writing style?
i really love my journalism class because it's super fun and engaging.
i know the local newspaper reporters don't have writing skills as good as me.
by taking journalism courses, one may be prepared for several exciting careers.
you know, working for a web design company is a really awesome thing to do.

“By taking journalism courses, one may be prepared for several exciting careers.” This is a formal writing style because it omits personal opinion, which eliminates “I really love my journalism class because it’s super fun and challenging,” because its your personal stance, and “I know the local newspaper reporters don’t have writing skills as good as me,” because you don’t know that they’re better because chances are they’re professionals and have more experience.
Second person is never professional and tends to be frowned upon, which eliminates the last statement of “you know, working for a web design company is a really awesome thing to do.”

Best thing to do, reread whatever you are writing on, and highlight things that are scientific or anecdotal. then pick which ever is easiest for you