In this case the aircraft has completed one cycle of service in the first 454 hours of service. Then making the difference between the hours of service and the hours of the first cycle we have:
Hours of the second cycle= Total time in service- time Airworthiness Directive
=468-454=14
Then we have 14 hours of service and need to accumulate the rest to complete 454. It is
454-14=440
Then we need to accumulate 440 hours additional to complete the Airworthiness Directive .
The original 12.50 is how much she pays each month regardless of rented movies, it is the 0 value and doesn't change. Each rented movie costs 5.25 (17.75-12.50=5.25) and that value would be multiplied by the amount of movies she rents that month, and then added onto the original base value.