Help with the master lock code

[Mathewm]

Hey,bought this og xbox secondhand so it's already got mods on it. Problem is it's also locked and I never got the lady's info to ask if she knew the code. Other problem is the way I've read to delete the settings I can't do. There's 2 accounts,master account and kids. The master account is locked,and 90% of the kids is locked. What do I do? Also I dont know how to do anything PC wise at all. Been trying this for almost 2 hours,really need help