15: Approximately it is 46.6%.
16: 7%(100%-65%-18%-10%)
Critical points is where the derivative (slope) is zero or does not exist. So to do this we have to find the derivative of our function:

So we apply chain rule:
=

Set our first derivative to zero and solve for x:
3(x^2 - 1) * 2x = 0
So we can see that (by plugging in) 0, -1 and 1 makes our solution true
So our critical value is x = 0, x = -1, x = 1
Answer:
Step-by-step explanation:
6/x^2 + 2 x = 7
2 x^3 - 7 x^2 = -6 (for x!=0)
(2 (x^3 - 3 x^2 + 3))/x^2 = 1
Divide 11.25 by (2/3). The answer is 16.875