For this you must use the Order of Operations.
First thing you do is divide: 9/3= 3. So once you rewrite it it should be like this 5-1-3-9. Start by going left to right. So start with 5 - 1 which is 4. then take 4 - 3 which is 1. Last but not least is 1 - 9 which is -8. So there is your answer, -8.
If you have any questions I am willing to help you ^^
Hope this helped! :)
~ShadowTheChimmiChanga