If Memory Deluge is copied, no mana was spent to cast the copy, so X will be 0. The amount of mana spent to cast the original spell is not copied. You won't look at any cards from your library as Memory Deluge resolves.
Memory Deluge
To determine the total cost of a spell, start with the mana cost or alternative cost (such as a flashback cost) you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell is determined only by its mana cost, no matter what the total cost to cast the spell was.
If an effect allows you to cast Memory Deluge without paying its mana cost, X will be 0. Memory Deluge will resolve, but you won't do anything.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Lake Hurwitz
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