The correct answer is:
The expression 9 miles ÷ 1 hour can be used to determine its speed
That is simply how we can calculate the speed if we divided distance by time e.g. in this case
If we divided 9 by 1 we will get 9, which will actually be the speed of the object.
Such simple calculations are used to determine everything from the estimated arrival time of a Train to the estimated arrival time of an International Flight.