We want to study the function represented with the given graph.
We will find that the constant of proportionality is r = $12.5
And the equation is:
c = $12.5*p
First, let's define a general proportional relationship.
It is written as:
c = r*p
Where r is the constant of proportionality.
a) Here we just want to get the value of the constant of proportionality, to do this, we just need to find a point on the graph.
By looking at the graph, we can see that 6 pizzas cost $75, then we can replace that in the proportional relationship to get:
$75 = r*6
$75/6 = r = $12.5
Then the proportional relationship is:
c = $12.5*p
If you want to learn more, you can read:
https://brainly.com/question/3314314