Answer:

Step-by-step explanation:
Let x be the number of miles.
We have been given that Sully's car has an average fuel economy of 28 miles per gallon. The capacity of the fuel tank is 16 gallons.
Let us find the number of miles that Sully can drive with 16 gallons.
This means that initially Sully's car has can drive 448 miles, so at x equals 0, y will be 448.
As the car consumes 1 gallon for each 28 miles driven, so the gallons of fuel consumed in traveling x miles will be 28x. As each gallon of fuel will decrease with each 28 miles traveled, so slope of our function will be -28.
Upon substituting slope and y-intercept in slope-intercept form (y=mx+b), we will get our function as:

Therefore, our required function will be:
.