Noelle goes east at N mph.
Karina travels west at N + 9
then their velocity between them is (N + N + 9)
After 8 hours they travel 8(2N + 9) = 232
(2N + 9) = 29
2N = 20
N = 10 mph for Noelle
N+9=19 mph for Karina
This would be a graph, a function is a straight line while a graph can be a scatter plot or something similar