you can do 280/40 would give you the answer for one minute, then whatever you get, multiply be 280, that is your answer for number 14.so it would be for every one minute you ride 7 miles. so it would be 7 miles times 20 minutes because you are calculating for an hour and we already have 40 minutes, it would give you 140 miles for 20 minutes, then you add 140 +280 which would give you your answer which is 420m/hr. if you read it step by step you would be able to understand.
