On a map, 1/2 inch represents 4/5 mile. what distance on the map represents 1 mile?

Here is the answer of the given question above.
Since it is given that 4/5 mile is equal to 1/2 inch, what we will be looking for how many inches will there be for 1 mile. 5/5 mile = 1 mile. 
This is how it would look like.
1/2 inch       x inch
          =       
..4/5 mile 1 mile 
Next, we cross multiply:
(1/2)1 = (4/5)x
Then divide both sides by 4/5. so we get
x = 0.025 inch
and that is 1/40 inch. Therefore, 1 mile is 1/40 inch. Hope this helps.