That depends on your definition of "whole numbers." In the positive integers, there are twenty pairs: (1, 39), (2, 38), ... (20, 20). If you allow zero, add (0, 40). If you allow negative numbers, there are an infinite number of pairs: (-1, 41), (-2, 42), (-3, 43)...
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That depends on your definition of "whole numbers."
In the positive integers, there are twenty pairs: (1, 39), (2, 38), ... (20, 20).
If you allow zero, add (0, 40).
If you allow negative numbers, there are an infinite number of pairs:
(-1, 41), (-2, 42), (-3, 43)...