What can you determine about the number of terms of the sum?

Iam so stuck. what is the worked out answer for this question?

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 does the sign of the slope tell you about a line?