Carter is deciding between two different movie streaming sites to subscribe to. Plan A costs $19 per month plus $2 per movie watched. Plan B costs $31 per month plus $0.50 per movie watched. Let AA represent the monthly cost of Plan A if Carter watches xx per month, and let BB represent the monthly cost of Plan B if Carter watches xx movies per month. Write an equation for each situation, in terms of x, and determine the interval of movies watched, x, for which Plan A is cheaper than Plan B.