Yes, dat werkt!
107.3a If a spell or activated ability has a mana cost, alternative cost, additional cost, and/or activation cost with an , [-X], or X in it, and the value of X isn’t defined by the text of that spell or ability, the controller of that spell or ability chooses and announces the value of X as part of casting the spell or activating the ability. (See rule 601, “Casting Spells.”) While a spell is on the stack, any X in its mana cost or in any alternative cost or additional cost it has equals the announced value. While an activated ability is on the stack, any X in its activation cost equals the announced value.

Triggert bijvoorbeeld een Curse of the Swine (als x 1 of meer is) ook het effect van deze kaart?

(Omdat bij de omschrijving van Curse of the Swine staat mana value = 2)