I will have to suggest that to them someday. It doesn't bode well to have me active to the point of exhaustion, after all.

X is not a literal living entity, but a representation of a missing variable within the given formula. For example, if you were asked to find the sum of six and and seven, X would represent the answer, which is unknown. The representative of this answer is not strictly limited to X, however. X is simply chosen most often because of its distinct appearance and, if the formula calls for another variable, it is often paired with Y because of their proximity in the alphabet. If you so desired, you could replace X with A or B-- or any other letter, really.