Of course, we're summing across many columns here, but the solution is to make many rows with the transpose tool and then sum across many rows:
![solution 434.png solution 434.png](https://community.alteryx.com/t5/image/serverpage/image-id/365254iD2B1B7ABFE0EE53C/image-size/large?v=v2&px=999)
One remark: I took the quick way out for the rename action of the percentage columns, since the unique identifier for all columns was 4 characters long. Otherwise, a regex or character function would be needed to determine the length of that identifier string.