Determine whether each equation represents a linear function. y= -x

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How do you do this geometry problem

How to find the exponential function y=ca^x, with points (1,2) and (2,1)

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?