Answer:

Step-by-step explanation:
Let is call
the price of the cereal box, and
its weight, then the linear equation of the price
as a function of weight
will be
,
where
is the slope of the linear equation, and
is the y-intercept.
We find
by evaluating the rise/ run of the linear equation:

thus we have

now we figure out
from the point ($5, 20 ounces):

So finally we have the function

which expresses the price of a box of cereal as a function of the number of ounces of cereal in the box