How to remove google apps from /data/data directory? Rooted (w/ SuperSU + TWRP Recovery) Nexus 7 (2012 Wifi, Grouper)

I am unable to remove apps from the /data/data folder on my tablet. When I remove them then reboot the system, they reappear. How do I permanently remove them? I tried deleted them from packages.list as well. 

Thanks
Ok. Thanks to @GiantTree for guiding me a bit. Here are the steps I performed to remove google apps from my Nexus 7. 


Enter TWRP Recovery
Click Mount
Check System
Then either navigate to /system/app/ and delete apps OR 
Open terminal on laptop, adb shell &amp; cd /system/app then rm -rf com.google.android.xyz


The key for me was MOUNTING THE SYSTEM PARTITION. Without that step, I was getting a failure.