Originally Posted by
emakarov Your graph corresponds to P = 50 - Q, while the correct relationship is P = 10 - Q/5.
Now, the question about slope is devious because the two axes have different scales. If the scales were the same, the slope would be equal to the coefficient of the independent variable, which is Q here, i.e., -1/5. Maybe this is what the question is asking. If you need the slope of the actual graph of P(Q) in these axes, then note that one square along the Q axis represents 10 units while one square along the P axis represents 5 units. Suppose the square side length is 1cm. If Q increases by 10, i.e., 1cm, then P decreases by -2 (since Q is multiplies by -1/5), i.e., -2/5cm. Therefore, the slope of the graph is -2/5cm / 1cm = -2/5..