If your life total is negative, X is considered to be 0.
September 12, 2019 5:44 a.m.
Note that the above is a change from older versions of the rules. I believe it changed sometime in the last 2-3 years.
September 12, 2019 10:23 a.m.
In the future, please remember to hit the green “mark as answer” button to indicate your question has been resolved. Since since this question has been answered for a couple of days, I have gone ahead and marked an answer on your behalf.