Basically, unit rates are special ratios with two different terms with two different units.
1. 3 inches of rain in 6 hours
Answer: 3 inches:6 hours
2. 70 miles in 2 hours
Answer: 70 miles:2 hours.
It's easy!
You didn't give a graph but I will visualize what it looks like for you.
The line is going through (0,-2) because that is the y-intercept.
The line has a slope of 3.
So, the line goes through:
(1,1)
(2,4)
(3,7)
(4,10)
(5,13)
The answer would be 6x/5-16/5