The exact value of sin (-270) is determined using the calculator in degrees mode. The answer is equal to 1. If the radians mode is used, -270 is equal to -2 pi/3. Hence using the calculator, we can verify that the answer is still 1. The value of -270 matters.
In order to get as many tickets they need 15 business class tickets and 12 economy class tickets (700x15=10,500)(375x12=4500) Which when you add those two makes 15,000.