Typically when a mobile device is locked, it wants the original e-mail account name and password XXXXX was setup with. If you can log into your account at https://mail.google.com/
that’s good, but it doesn’t guarantee it’s the same account the tablet is using or the original password XXXXX
If you don’t remember the username and the account was properly setup at creation time, you can recover the name using "I forgot my username" here: http://support.google.com/mail/bin/answer.py?hl=en&answer=46346
And here’s a trick to recover an account name on an Android device: https://productforums.google.com/d/topic/gmail/ydNElvUjJVU/discussion
If you have the username, the following will help with the process to recover the account by resetting the password: http://gmailaccountrecovery.blogspot.com/
BUT... A recovered account won't have the original password XXXXX is what the device needs to be unlocked. In that case the device will probably need to have a factory reset done and then setup again with an e-mail account (be sure to write the information down this time). If it's setup with the recovered e-mail account, any purchased apps and synced data should be restored. If a new account needs to be created, all previous information will be lost.
If this is a maze pattern lock then a reset of the tablet will need to be done.
There is one way but it is a very complicated way. Maybe you might know someone who can give this a try. http://chethaka.wordpress.com/2013/02/28/unlock-an-android-device/
If all fails and you choose to do a factory restore
Hold the volume down and the power tell you see the lenovo logo and let go.
It should then boot into recover mode.
Or check your user manual that came with this tablet for specific instructions on how to hard reset.