51.2,64,80, (), () find the rule and fill in the number. How to write? And (), (), 19.8,13.2,8.8 also find the rule and fill in the number, how to write?

51.2,64,80, (), () find the rule and fill in the number. How to write? And (), (), 19.8,13.2,8.8 also find the rule and fill in the number, how to write?

38.7-28.6-19.8-13.2-8.8