Peppermint 10 change password

I'm fairly new to linux. Installed Peppermint 10 on my buddies laptop. It was working really well. No one touched it for the last 2-3 months. I started it up yesterday. There are 275 updates. When I click install it asks for a password. My buddy doesn't remember it.

I tried a few tutorials for changing the password. Here are the last two:
https://www.tecmint.com/reset-forgot...in-linux-mint/
and
https://www.howtogeek.com/howto/linu...nutes-or-less/

Both of these gave me the message the password was changed, but it wasn't. I'd sure appreciate a link to a tutorial that works.

Thanks