Help, college algebra

What is the average rate of change for this function for the interval from x=2 to x=4 ?

What numbers are included in the set of integers? what numbers are not included?

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?