How do I reset system/administrator password?

I got a Dell Latitude 10 ST2e tablet at a yard sale. Previous owner said it worked fine until kids locked her out. No clue about password. When it powers up it has a black screen with a blue input box asking for System or Administrator password. There is a service tag # 7H13RT1 above the input box.

Is there a Master password?

Can this password lock be undone?

I would appreciate any help.