Depends on what you enjoy more (which one is less crap then the other) / get better marks in and (if applicable) which of these subjects relates to what you want to study after you finish year 12. I would keep business and drop modern.
Based on the information that you've given us I would say keep both, however, consider
- Teacher quality
- Number of students in previous years getting band 6s, 5s etc in respective subjects
- Your ranking/marks for the respective subjects
- How you are performing in your other subjects (ranks/how well your school performs in the subjects)