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: ['D', 'G', '9895', '143', '37', 'S', '1539', 'x', 'a', 'x', 'B', 'i', '9719', '839']

SOLUTION: 22172

PROBLEM: ['8669', '9115', '2573', '9261']

SOLUTION: 29618

PROBLEM: ['2863', '4287', 'o', '2501', 'f', 'R']

SOLUTION:
9651