Question

I have a string like 30+20%. Now I want to replace 20% with (20/100). Thats it.

Answer 1

If the percent doesn’t occur in any other situation in the string, you don’t even need a regular expression:

s = s.Replace("%", "/100");

To add the parentheses you need the regular expression though:

s = Regex.Replace(s, @"(\d{1,3})%", "($1/100)");