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.
['339', 'h', 'd', '7449', 'e', 'u', '5055', '7029', '9009', 'G', 'U', '3', '441', '3273', 'K', '3827', '7069', 'x']