Yes, y=-9x is proportional
3,322.609847222222 mph. First covert miles to km. This distance is 239227.909 miles. then divide this by the number of hours which is number of days times 24. It took 3 days so it is 72 hours. After diving 239227.909/72 you get your answer of 3,322.609847222222 mph
6/y=9/5(due to similarity)
y=6*5/9=30/9=10/3=3.333..
