Final answer:
To find out how many Husky Cards William still needs to sell, subtract the number of cards he has already sold from the total number of cards he needs to sell. In this case, William needs to sell 25 cards and has already sold 9 cards, so he still needs to sell 16 cards.
Step-by-step explanation:
To determine how many Husky Cards William still needs to sell, we subtract the number of cards he has already sold from the total number of cards he needs to sell. In this case, William needs to sell 25 cards and has already sold 9 cards. So the equation to model this situation is 25 - 9 = 16. William still needs to sell 16 Husky Cards.
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