Answer:
If you really meant that the number of dogs is 12 greater than 3 times the number of cats then:
3 cats
Step-by-step explanation:
21= number of dogs
c = number of cats
21 = 12 + (3c)
3c = 9
c = 3
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
D because of the distribution property
If 1 inch is .25 miles then all you have to do is multiply .25 miles by 5 inches and u get 1.25 miles.