i can not access my apple air model 2012

[stiv2us]

when trying to open my mac air it now comes up asking for a key number this must have been put in be the last owner but i can no longer get iin touch with her the mac air works perfect but need the 4 digit code to open has any one got advise ..EMAIL REDACTED - SS

 

[RealBeast]

Sorry, but forum rules prohibit assistance with password related issues.