If Eugene used all but 16 of the 52 cards, then he used 52-16=<<52-16=36>>36 cards.
If for every card he used 75 toothpicks, then a box of toothpicks would have enough toothpicks for 450/75=<<450/75=6>>6 cards.
Since one box has enough toothpicks for 6 cards, then for 36 cards he would need 36/6=<<36/6=6>>6 boxes of toothpicks.
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