Final answer:
To find out how long Brad has been in his book club, you divide the total books read by the average number of books per month. However, the calculated result does not match the provided options, suggesting a possible error in the question itself.
Step-by-step explanation:
The student is asking how many months Brad has been with his book club given that he has read a total of 84 books. Since it is mentioned that Brad read a total of 12 books over seven months, we calculate the average number of books Brad reads per month by dividing 12 books by 7 months, which equals approximately 1.71 books per month. To determine how many months he has been with his book club, we divide the total number of books he has read (84 books) by the average number of books per month (1.71), which gives us approximately 49 months. However, since this number isn't presented in the multiple-choice options provided in the question, there may be an error in the question's details or a misinterpretation of the information given.