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.
['1281', '573', 'G', '8945', '9801', 'x', '6481', 'Y', '2359', '7759', '8209', '2875', '4869', '257', 'C', '1665', '7927', '7']