TASK DEFINITION: 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.
PROBLEM: ['7067', 'E', 'C', '1879', 'Z', 'u', 't', '2053', '6769', 'r', '5207', '7009', 'H', '5587', 'i', 'M', '1357', 'A']

SOLUTION: 36928

PROBLEM: ['l', '5369', 'z', 'U', 's', '2357', '3367', 't', '6539', 'K', 'a', 'Q', 'x', 'e', '6459', 'K', 'B', 'f', 'j']

SOLUTION: 24091

PROBLEM: ['x', '4835', '8169']

SOLUTION:
13004