Explain how you could convert a rate of 18000 miles per hour to miles per second

You could multiply that fraction by (1 hour / 3,600 seconds) .

               (18,000 mile / 1 hour) x (1 hour / 3,600 second) = 

               (18,000 x 1) / (1 x 3,600)  (mile-hour) / (hour-second) = 

                     (18,000 / 3,600)  (mile / second)  =  5 mile/second

18000 miles / 1 hour)(1 hour / 60 minutes)(1 minute / 60 seconds) =

18000 miles / 3600 seconds =

5 miles / 1 second

5 miles per second

The length is 23 and y because you add them together