Answer: the answer is b.
r = 0 means that there is not a linear relationship between both variables, but there are other types of relationships that can be happening here.
you for example can have a quadratic relation or something weirder.
A variable is an unknown like x so
first we start with
x=8
then we subtract (because you must add to reverse subtraction)
x-2=8-2
x-2=6
then we divide ( because you must multiply to reverse division)
(x-2)/3=6/3
(x-2)/3=2
find x
Unsure of what you mean by "reference number."
I do recognize that 11pi/9 is in quadrant III. I suspect that the so-called "reference number" is the acute angle between the end ray of 11pi/9 and pi, or, in more easily comparable numbers, between 9pi/9 and 11pi/9.
That difference is 2pi/9.
Let us assume the number of student's in Zoe's class = x
Then
Number of students that have pets = 4x/5
Number of students that have rodents as pets = (1/8) * (4x/5)
= x/10
Number of students in Zoe's class
that have pets that are not rodents = (4x/5) - (x/10)
= (8x - x)/10
= 7x/10
I hope that the procedure is clear enough for you to understand and this is the answer that you were looking for.