This article describes how to perform a factory reset.
INSTRUCTIONS & INFO
A master reset reverts the device back to factory settings. It will permanently erase all personal data, preferences, settings and content such as pictures, ringtones and apps that are saved to the device. Data stored to an SD card will not be erased unless otherwise selected. It is recommended that you save (backup) important data to your SIM, SD card, or a computer before proceeding.
To perform a master reset, tap the Settings icon.
Scroll to, then tap Backup & reset.
Tap Factory data reset.
Tap Reset tablet.
Enter the four-digit code, then tap Erase everything. Note: If unable to reset the device using the above steps, try the alternate master reset method by first powering the device Off. With the phone powered off, press and hold the Volume up and Power keys together until the "ASUS" logo displays (3-4 seconds), then release them. Press the Volume down key until "Recovery" is highlighted and then press the Power key. The device will restart. Press the Volume down key until "wipe data/factory reset" is highlighted, and then press the Power key. Press the Volume down key until "Yes - delete all user data" is highlighted, and then press the Power key. Press the Power key to select "Reboot system now".