Hello!  I'm completely new to Salesforce and need help.  Read a lot of the discussions but can't figure out what I need. 

Okay, so I have a picklist field named 'Action' with various options.. I'll just call them Option 1, 2, 3, etc. 

I need a formula that would do this: 
((Total of all options - (Option 1, Option 4 & Option 7)) / (Total of all options - Option 3) = %

Help!! Please :)