I would say D, determine if it can be factored by grouping (sorry, I forgot to put in the answer here).
The question can be written out like this:
36 = 0.009x
Multiply both sides by 1,000:
9x = 36,000
Divide both sides by 9:
x = 4,000
P=1/5. factor out the p to get 4p-15pn=4/5p-3n and just solve to get p=1/5