She can fit 3 squares along the 10 inch side and 6 squares along the 18 inch side. When you multiply 3 by 6 you get 18. The answer is not 20 because you cannot fit 20 3x3 squares.
c) It will require the United States to spend money to defend the islands.
Explanation:
Carnegie believes that conquering the Philippines would cost the US money because it will require the US to spend money defending the islands from foreign invasion.