In this question, you want to know the number of weeks left until vacation knowing that the number of days left until vacation is 28 days.
Now, we know that 1 week is 7 days and we want to know how many weeks are in 28 days, we can simply use cross multiplication to calculate the number of weeks as follows:
number of weeks in 28 days = (28 x 1) / 7 = 4 weeks
Therefore, 4 weeks are left until vacation.