Here, to find the average rate of change, you would simply divide 270 by 63. And when that is done, you would get a long decimal. 4.285714285714286
And since you obviously can't put in such a long decimal as your answer, you would round it instead. Once rounded, you would end up with 4.29 (because the number after 8 is five, which rounds up, which would turn the 8 to 9.)
For the answer to the question above,
since the only variable used to determine earnings is the number of doors knocked, you can eliminate options 1 and 3 as they are based on the number of books sold, which is not a part of the equation.
That leaves the only options being the increase of $20 or $50 for each door knocked. As the x value we multiply by 20, the correct answer is #2, her earnings will increase by $20 for each door knocked.
You can also check this by plugging in values:
Assume 10 doors are knocked:
E(10) = 20(10)-50 = 200-50 = 150
Assume 11 doors (1 more door) is knocked:
E(11) = 20(11)-50 = 220-50 = 170
<span>The increase from 1 door is $20. the answer is B</span>
0.77 is the answer to your question