First in order to solve you need to get rid of the fraction. You can do so by multiplying to entire equation by the denominator like so...
5(5r - 1/5) = (4/5)5
25r - 1 = 4
Then to isolate the variable you need to add 1 to both sides.
25r = 5
Then you divide.
r = 5/25
Simplify.
r = 1/5
I hope this helps love! :)