Dawson purchased 20 shares of stock for $18 a sshare in a technolgy company. Three years later ,he sold all of the stock at a price of $21 per share. What percentage return did dawson make on this stock

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?