How do you get the answer for 10x4= _ x 5

How can you decide witch operations to use to slice a two step equation

Rectangle leg this 11feet and perimeter of 38feet what is the width of the rectangle in feet

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?