You run 7 miles in one hour and 21 miles in three hours what’s the rate of change

If you run 7 miles in 1 hour, that is your rate of change. When the independent is at one, that is your rate of change. We can see the rate of change does not change. I also run 21 miles in three hours. If we divide y by x, we get the same number as compared to one mile. So, the rate of change is 7 miles as each hour passes.

I’m not absolutely sure but i think it’s 7x6x5x4x3x2=5040 because as the first character you can take any of the 7 given then you are left with 5 then 6 then 4 etc.