Answer:
The rate of change is "-3". Which means the rate at which the tractor uses fuel.
Explanation:
The equation describes a line and any line follows the equation:
y = m*x + c
Where "m" is the rate of change and "c" is the shift on the line. Comparing the equation for the fuel and the equation from the line, the rate of change must be "-3". The rate of change in this context describes the speed at which the tractor uses fuel, at a rate of 3 gallons per hour.