Your first step should be to plug in the q and f values they give you. q being 20 and f being 16. From there you want to isolate 1/p by subtracting the 1/20 from both sides. You should be left with 1/p = 1/16 - 1/20. This will come out to be 1/80 or 0.0125. Now that one side is 1/p and the other is 1/80 you can multiply both sides by p in order to get 1=1/80 times p which means that p = 80 . Hope this helps
