Various simple rename presets has a couple of very similar examples to that, while RegExp basics: Removing characters from start/end of names should help you learn the basics of regular expressions to let you modify the examples if what you want is slightly different.
The only thing complex about your example is that you have a [ character in your original filenames. Since [ has special meaning in regular expressions, you need to "escape" it with \ and use [ where you want to match a [ character (like I did in my post above). Beyond that it's basic regexp stuff.
Give it a try and we'll help you learn how to use regexps yourself.