There are infinitely many possible answers.
Two ways to look at that:
Pick any number - integer, rational, irrational : positive or negative. You can even pick a complex number, if you know what that is. Call this number x.
Let y = negative x minus 8 = -x - 8
Then x + y = x + (-x - 8) = x - x - 8 = -8
Since x was any one of infinitely many numbers there are infinitely many pairs of number that sum to -8.
ALTERNATIVELY
Consider
(1, - 9), (2, -10), (3, -11), ...
Then add 0.1 to all numbers
(1.1, -9.1), (2.1, -10.1),
and then 0.2, and 0.3, 0.4 etc.
Then go for two decimal places, 3 dp, 4 dp, ...
There can be infinitely many decimal places.
So again, you have infinitely many pairs.
the products
260 and 7
1 and 749, when added together.
0 and 49, added together.
125 and 1, added together.
0 and 114 added together.
52.5, when added together.
11+11
It is impossible.
These numbers added together make the 1000th triangle number, which is 500,500.
They make a rational number.
9 and 36