My computer has no admin user
Solution 1:
Boot into single user mode.
Delete the file /var/db/.AppleSetupDone and then type exit and press return
At that point, the system will boot back to the normal setup process (keeping your old users intact) You will be guided through the steps to create a new admin user so pick a short name that doesn't exist on the Mac and you can then re-grant your normal user admin rights if you wish.