p: If every fourth card drawn is a spade, then 25% of the cards in a deck would be spades. If 25% of the cards in a deck are spades, then every fourth card drawn would be a spade. If every fourth card drawn isn’t a spade, then 25% of the cards in a deck aren’t spades. If 25% of the cards in a deck aren’t spades, then every fourth card drawn wouldn’t be a spade. If every fourth card drawn isn’t a spade, then 75% of the cards in a deck are spades.