The picture is too blurry for me even when I try zooming in on it
There is a problem with your question. it doesn't make sense ???
The point of inflection is calculated by equating the second derivative to zero and determining x from there.
f"(x) = -x²2xsinx² + cosx²(2x) = 0
2xcosx² - 2x³sinx² = 0
2x (cosx² - xsinx²) = 0
2x = 0 ⇒ x = 0
cosx² - xsinx² = 0 ⇒ x = 3.82 (if you use shift+solve in your scientific calculator)
Thus, the function only has 1 point of inflection and it is at x = 0.
10 3/5=10.6
10.6+12.5=23.1
35.0-23.1=11.9
It is 11.9 miles from Chester to Durbin.