Final answer:
The slope (m) in the equation y = 280 - 40x is -40, which matches option A) m = -40 because the coefficient of x is the slope in the equation of a line.
Step-by-step explanation:
The slope (m) in the equation y = 280 - 40x is found by identifying the coefficient of the x variable when the equation is in the form y = mx + b.
In this standard form of a linear equation, m represents the slope, defined as the rise divided by the run, and b represents the y-intercept, which is the point where the line crosses the y-axis. The given equation already has a coefficient of -40 in front of the x variable. Therefore, the slope of the graph is m = -40, which corresponds to option A) m = -40.