## Arithmetic on lists within lists

I want to take a nested list and replace each sub-list with an arithmetic operation on its elements. For example: a={{1,3},{2,2},{2,3}}. I want to get {4,4,5}. I can do it by: f{x_,y_}=x+y and then Map[f,a] but I suspect that there has to be an easier way by applying rules or similar.