Cassandra is comparing two different subscription plans for a streaming service. The plans have a promotional decreasing cost. The basic plan starts at $ 18 for the first month and decreases by $ 1 for each subsequent month, represented by the equation y = 18 − x . The premium plan costs 1.25 times the monthly cost of the basic plan, which is represented by the equation x = 1.25 y . After how many months will the costs of both plans will be equal? Enter your answer in the box.