Mr. White doubts that the monkey's paw can really grant wishes.
It would be this because Mr. White is in a way fighting with his mind.
Answer:
私の姉妹の名前はヤハイラです、彼女は18歳ですか?or
Watashi no shimai no namae wa yahairadesu, kanojo wa 18-saidesu ka?
Explanation:
It would be 2.5% because you would set it up as 0.5=p x 20 you divide each side by 20 which should equal 0.025. you move the decimal two places to the right so p actually equals 2.5%