A salesperson at a jewelry store earns 3% commission each week. Last week, Heidi sold $ 640 worth of jewelry. How much did she make in commission? How much did the jewelry store make from her sales?

Me with this assignment ! i only partially understand, so explain. also it's a work sample. at the championship bike race, steve and paula were fighting for first place. steve was 175 feet ahead of paula and had only 300 feet left to go. he was very tired and was going only 9 feet per second. paula was desperate to catch up and was going 15 feet per second. who won the bike race and by how far did she/he win?