If a creature has multiple instances of amplify, each one works separately.
July 13, 2013 · Magic 2014
If a creature has multiple instances of provoke, each triggers separately.
June 17, 2011 · Commander 2011
If a spell has multiple instances of storm, each triggers separately.
April 1, 2011 · Duel Decks: Knights vs. Dragons
The affinity ability reduces only the amount of generic mana a spell's controller has to pay; it doesn't reduce how much colored mana that player has to pay.
February 4, 2011 · Mirrodin Besieged
The affinity ability reduces only the amount of generic mana a spell’s controller has to pay; it doesn’t reduce how much colored mana that player has to pay.
October 1, 2010 · Scars of Mirrodin
The affinity ability reduces only the amount of generic mana a spell’s controller has to pay;
February 1, 2010 · Worldwake
The affinity ability reduces only the amount of generic mana a spell's controller has to pay; it doesn't reduce how much colored mana that player has to pay.