Https://www.codecademy.com/courses/learn-r/lessons/r-data-frames-modifying/exercises/review

Hello. I keep getting the wrong answer but whenever I check the answer its the same thing that I have just the format/spacing is different. Now I am getting confused on how to properly write my code.

It’s asking you for the DIFFERENCE (-) in rank 16 to 15. It needs to be written as: rank_2016 - rank_2015