Karen took out a loan for $725 with a 2.5% interest rate that is compounded annually. No additional money will be deposited or withdrawn from the account. How much in interest will Karen pay back at the end of 18 months?

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?