How much potassium does a sample have

Question

The number the ratio of nitrogen to potassium in a sample of soil is 12 to 9 the sample has 36 units of nitrogen 

Answer 1

12 nitrogen/9 potassium = 36 nitrogen/x potassium

12x = 9x36

12x = 324

x = 324/12

x = 27 parts potassium