The water level in a full water tank changes by the same amount each day when the tank gets a leak. the total change in the water level is -128 gallons after 16 days. what was the daily change in the amount of water in the water tank

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?