Replace Number in TextEdit with 1/3 of that number

I don't see any parentheses in your document. Did you mean double-quotes?

IAC, your new question is related, but materially different from your original quesiton.
Please repost your new question in a new Topic as follows:

  1. Clarify how the numbers you want to use are located
  2. Post real-world example of your source text using the forum Code Block
  3. Post example of the results of the changes you want to make, also in a Code Block.