Let's find how many days Carole works:
If she works 6/7 of 28 days, Carole works:
[tex]\frac{6}{7}*28=24\text{ }days[/tex]Let's find how many days Carole does not work:
The non-work days is the difference:
[tex]28-24=4\text{ days}[/tex]If Carole goes to class on her non-workdays, she goes to school 4 days.
Answer: b. 4.