In this task, you are given an input list A. You need to find all the elements of the list that are numbers and calculate their sum.
['g', 'y', '7811', 'J', 'b', 'e', 'G', 'H', '5715', 'E', 'q', 'Z', 'r', '159', '9131', 'j', 'Q', 'b', 't', '51']