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.
['6907', '9123', 'L', '8871', 'q', 'C', 'U', '7403', 'F', '3827', '3951', '8879', '2865', 'x', '6175', 'T', '1147']