BIOS or Operating System's passwords are there for the purpose related to Security and Privacy to protect the legitimate owner of a machine. While there are many locations on the Internet that might help you learn about managing passwords for a machine's BIOS or Operating System, we a G2G do not assist in what amounts to hacking past a machine's Security and Privacy safeguards.
While such requests are often legitimate, and come from users who experience exactly the kind of problem that you post, we have no way of determining legitimate vs. not legitimate, therefore we do not respond to such requests.
Your best course of action is to ask the person that passed on the tablet to access the device and you then change the password to something of your own, if that is not possible, take the tablet to a local tech or tech store and have them see if they can access the device, you will need proof of ownership such as the sales receipt, picture ID such as a driving licence or passport and a utility bill that has your address on it.