The rate of change is the slope. You're finding the average between two points, so find the slope between them using the slope formula. It's 20.
Step-by-step explanation:
[tex]m = \frac{y - y1}{x - x1} [/tex]
m is the slope.
plug in the numbers, and you get
[tex] \frac{300 - 200}{6 - 1} = \frac{100}{5} = 20 [/tex]
