How to erase more than 20 messages at a time in Gmail

1. After you had made your search on gmail, or you have found the emails that you want to erase using the filters, Select all the messages that are visible (20)
   
    
2. Click on "Select all messages that match this search"
   
    
3. Erase all the emails.
    

If you don't want to erase them you can also archive them or mark them all as read, click here to learn more.