Can some one help me please?

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

Sarah took the advertising department from her company on a round trip to meet with a potential client. including sarah a total of 11 people took the trip. she was able to purchase coach tickets for $280 and first class tickets for $1280. she used her total budget for airfare for the trip, which was $6080. how many first class tickets did she buy? how many coach tickets did she buy?

What is the slope of the line that passes through the points (–9, 2) and (0, 4)? the slope of the line is