17.The singular form of the word "dice" is "die". Tom was throwing a six-sided die. The first time he threw, he got a three; the second time he threw, he got a three again. What's the probability of getting a three at the third time?

18. Rachel was flipping a coin with Jerry. She told jerry: "I am able to get all heads in two tosses." Jerry laughed at her: "No, the probability of getting two heads at two tosses is only__"

20. Laura and Melissa were playing dice. What the probability of Laura and Melissa both getting a 6?