Input is domain and output is co-domain.
An expression is said to be a function if for every input, there is only one output. In table B, for every input, you get different outputs. Therefore, table B is a function.
The number "4" is in the hundreds place. To the right is 7, and since it's greater than five it rounds up. So 16,473 to the nearest hundred is 16,500. Hope this helped!
16. 4 (9*4=36)
17. 6 (6*11=66)
18. 8 (10*8=80)
19. 9 (9*5=45)
20. 48 (4*12=48)
21. 13 (13*2=26)
