A cyclist is riding from the city to the country. She rides 20 miles each hour. At
the beginning of the 1st hour, she is 10
miles away from the city center. At the
beginning of the 2nd hour, she is 30 miles
away from the city center. Write an explicit
formula to show her distance from the city
at any given hour. Then use the formula to
find her distance at the beginning of the 5th
hour.