Two sailboats are traveling along the same path away from
a dock, beginning from different locations at the same
time. John's boat begins 15 miles from the dock and is 45
miles from the dock after 5 hours. The distance of
Roberta's boat from the dock is represented by the
function y = 5x + 20, where x represents time, in hours, and
y represents the distance, in miles, from the dock.