100
20 of them
3 pairs of whole numbers add up to 7: 1 +6, 2+5, 3+4 (0+7 also equals 7, but zero is not a whole number)
6
49 of them.
100
20 of them
An infinite number.
3 pairs of whole numbers add up to 7: 1 +6, 2+5, 3+4 (0+7 also equals 7, but zero is not a whole number)
6
There are infinitely many pairs of numbers that sum to 59. One such is 0.1 and 58.9
49 of them.
There 4 pairs of primes that can give a sum 40 in addition. They are (3,37), (11,29), (17,23),(19,21).
100
Only one pair.
Just 3 + 3
The sum of two numbers is a whole number if both of the numbers are whole numbers, or if the sum of two fractions can be simplified to a whole number.