Here, sadly, is where I have to take the side of those who pray, sort of.
So, X is of the opinion science alone has been responsible for advances in medical science, such as diagnostics, treating injuries, fighting infections, all the way up to nearly eradicating some diseases such as smallpox, leprosy, plague, and so on. And actually, I agree with him, and more - some of these advances were made in spite of religion. However, playing the devil's advocate here for a moment...
There is no way to prove, or disprove, whether or not prayer had anything to do with the advances in medical science. First of all, when the Bible speaks of answering prayer, a.) It does not assure you you will get the answer you want; sometimes the answer is NO; and b.) The answer may not come right away. So, say, all those people who prayed for an end to leprosy, who's to say they didn't get it? Maybe not in time for them, or their loved one who had it, but here we are. Same for smallpox, infections, and on and on. So one cannot categorically state that prayer doesn't work. Of course, the opposite is true as well.
That's the advantage of at one time being one of 'them' and studying for the ministry - I can see both sides. My choice, however, is my own.
Carry on.