If you don't have an Internet connection, the only way to unlock your tablet it to do a factory reset of it. It can be done by turning it off. After the tablet is off, try to press the Volume and the Power buttons simultaneously. Hold them pressed until you see an Android screen. By doing this you will enter the recovery menu. You can navigate through it using the Return key for down and the Power button for up. To select the Factory Reset / Data Wipe option you should press the Volume Up button. Notice, that by doing this, you will wipe all the data from the tablet and restore it to its factory configuration. However, this will unlock it.