Mag X and DRE

[Ajax]

if i have a Magmortar X and 2 fire energies and a DRE and i use Flame bluster, does it do one hundred or 90 if i discard the DRE thanks in advance

 

[PokePop]

90. You calculate the damage before the discard is done.

Note that if you discard the DRE, you would still have to also discard one of the Fire energy cards.
This is due to an errata that was issued for this card.
It can be found in the Compendium EX (and the upcoming Compendium LVX).