posted by Erin .
Sue was in excellent shape in high school, she could ride her 10-speed bicycle 4.8miles to her grandmother's house in 11 minutes. Her return trip home took 14 minutes. The times are different due to there being a slight downhill slop on part of the trip to her grandmothers. If sue was able to ride her bike on a perfectly flat surgace with no hills, how fast can he travle in miles/hour?