If I understand that you are looking for a Dax formula, try Accuracy = Divide([No Class Change], [Class Change] + [No Class Change]). For the first line in your matrix, you would have the result below.
If this solves your issue, please mark this as the solution. Kudos are nice too!
Not sure what you are asking...should be the same with 1 or 0. Just reference the column name. Divide will return a blank unless you give it an alternative return for a divide by zero. See Dax Divide on the web: