Car Rental
A company rents cars for 5-day or 7-day blocks only. For example, the company can rent cars for 17 days ( 2 x 5 + 7 ) but not 18 days because there are no multiples of 5 and 7 that add to 18.
Would a person be able to rent the car until December 31 starting from any date between January 1 and November 30?
Support your answer with mathematical equations or calculations.