There are an infinite number of pairs:
(7, 8), (6, 9), (5, 10), ... , (0, 15), (-1, 16), (-2, 17), etc
then (7.1, 7.9), (6.1, 8.9), (5.1, 9.9), ... etc
and (7.2, 7.8), etc
and (7.3, 7.7), etc
etc
and then to 2 decimal places etc.
And then there are Irrational Numbers.
The two numbers that add up to 15 are 7 and 8. This is because 7 + 8 = 15. In mathematics, this is known as an addition problem, where two numbers are combined to find their total sum.
31
23
33
110 and -95
30
90
30
55
-23
51
29
79