Because it starts at 11:30 AM, we know that the initial snow depth is 0 at x=0.
I'm not sure if it's 9 inches total but I will solve it as if it was. Thus, 11:30 AM to 7:30 PM is 8 hours. 9 inches/8 hours= 9/8 inches per hour.
The function should be y=9/8x.
We can check this answer:
after 1 hr (x=1) : 9/8
x=2: 18/8
x=3: 27/8
x=4: 36/8
....
x=8: 72/8= 9 inches