Answer: 9 is what I am thinking.
Explanation: So, first you have to know that 2/3 + 1/3 = 3/3 = 1 cup. The answer is 1 and 1/2 cups will make 1 cup when using a 2/3 cup. So, then 1 + 1 + 1 6 times equals 6, then 1/2 + 1/2 6 times equals 3 and 6+3 = 9. There's your answer.