Juanita wants to participate in a 20 kilometer bicycle race. she is considering two training programs below.
program a: ride 10 kilometers on the first day and increase the distance by 500 meters each day.
program b: ride 7,500 meters on the first day and increase the distance by an additional 0.75 kilometer each day.
if juanita chooses program a, on which day will she ride 15 kilometers for the first time?