No sideboard cards are available to bring in for this matchup, so the 75 stays the same. Against Affinity, Wear // Tear and Meltdown are your best mainboard tools, with Meltdown able to wipe out cheap artifacts like Mishra's Bauble, Mox Opal, and Welding Jar for a low X cost. Thraben Charm can also destroy an enchantment like Weapons Manufacturing. Prioritize killing Kappa Cannoneer with Galvanic Discharge before it grows out of range, and race with Ragavan, Nimble Pilferer and Ocelot Pride since Affinity often lacks direct interaction for your creatures.