Magic: The Gathering Comprehensive Rules Changes - Planar Chaos to Future Sight

Old rule (Planar Chaos)	New rule (Future Sight)
203.3b. [Click to view all changes.]
	203.3b. When calculating the converted mana cost of an object with an {X} in its mana cost, X is treated as 0 while the object is not on the stack, and X is treated as the number chosen for it while the object is on the stack.

Old rule (Planar Chaos)

New rule (Future Sight)

203.3b.

When calculating the converted mana cost of an object with an {X} in its mana cost, X is treated as 0 while the object is not on the stack, and X is treated as the number chosen for it while the object is on the stack.