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Open Firefox. In Firefox, click the menu button (the three lines button at top right) and choose Add-ons. The Add-ons Manager tab will open. In the Add-ons Manager tab, select the Extensions option. Select the Ask add-on you see there. Click its Disable button or delete it (you can also open Add on window from Tools menu > Add Ons)
After removing the Ask, close the Window. Then in Firefox, click on menu button again and choose Options. Select the General panel. Under "Home Page", change the home page to www.google.com
Restart Firefox. Please let me know if that didn't work, so we can continue troubleshooting.
You can also access Add-ons manager by pressing Command, Shift and A buttons at same time or from Tools menu in the top bar. Then in there, click Extension and if you see Ask toolbar, delete or uninstall it.
Then close that window. Then click on Firefox menu at the top left and select Preferences or press Command and , keys at same time and this will bring Preferences.
Under General section, change the Home page to www.google.com or any page you wish. If you want to restore it to default, click Restore to Default button and this will remove Ask webpage.