Answer:Fred has 13 9/10 minutes left for question C
Explanation:
The total time that Fred has to do the three-problem quiz is 30 minutes.
He spent 10 7/10 minutes on question A. Converting 10 7/10 minutes to improper fraction, it becomes 107/10 minutes.
He spent 5 2/5 minutes on question B. Converting 5 2/5 minutes to improper fraction, it becomes 27/5 minutes.
Total time that Fred spent on question A and question B is
107/10 + 27/5 = (107 + 54)/10
= 161/10 minutes.
The amount of time that he has left for question C would be
30 - 161/10 = (300 - 161)/10 = 139/10
= 13 9/10 minutes