What pairs of numbers that would satisfy the statement:the sum of 2 numbees is 18

There is an infinite number of such pairs. Even if you consider just the integers, there is still an infinite number of pairs. If you limit the number in the pairs to whole numbers, then here are the pairs:

0, 18

1, 17

2, 16

3, 15

4, 14

5, 13

6, 12

7, 11

8, 10

9, 9