Can't delete backups
I now have quite a few backups of my MacBook in the trash been. They were originally on my external hard drive, which I use for other things, and when I deleted them to free up some space they appear in the trash bin of my Mac. I have been unsuccessful at any attempts to completely delete these backups in the trash. After about five minutes it says, "The operation can't be completed because an unexpected error occurred (error code -8072)."
In addition to this it requires the administrator password whenever I want to do anything as far as folders or delete items in the trash. I'm fairly new to the world of Mac, and my searches haven't uncovered any help. I was hoping maybe respondents to this post would give me some clues.
MacBook Pro, iOS 10.2.1, macOS Sierra Version 10.12.3