Answer:
30, or 42
Explanation:
If they took 12 quizzes over the course of 2 weeks, then we can assume that they take 6 quizzes each week (12/2 = 6).
Over the course of 5 weeks, they'll have taken 30 quizzes if the above is true. However, the 'or' is there because I don't know if they're including the past 12 or not. If they are including the 12 quizzes taken over 2 weeks, then the answer is 42. If they are only referring to the 5 weeks of school, then the answer is 30.