Finally a complete riddle! We get a title, an image, some text and one more file to work with. Everything is relevant, with the title containing most of the hints and information.
This riddle is quite tricky, as it requires you to do two things that you have never done before. The first is that the answer ends with .php and not .html. The second is that you'll need to find a file that ends with .txt, which, apparently, is hinted to with the 'Textual' in the title. Once you know this, the riddle is quite easy. Otherwise, it is really hard and time consuming.
Once you have the text file, figure out the value of 'x', calculate the answer, convert it to the correct format, and you're done. Pretty easy, eh?
You will need the text, title and image to find 'x'. You will know when you calculate the right answer, as it is a pretty significant number.
Note: The answer is in capital letters, and ends in .php.
Look at the title. It is not 'Life 17' but 'Life XVII'. The answer is in roman numerals.
To get 'x', use the second word in the title (proof), and the text hinting at alcohol, and apply it to the image. From wikipedia:'Alcoholic proof is a measure of how much ethanol is in an alcoholic beverage, and is approximately twice the percentage of alcohol by volume'.