When Nicole left her house in the morning, her cell phone battery was partially charged. The charge remaining in Nicole's battery, as a percentage, can be modeled by the equation B=-9t+72, where t is the number of hours since Nicole left her house. What is the slope of the equation and what is its interpretation in the context of the problem?

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?