Answer:
Just subtract, 400 - 50 = 350, 350 - 50 = 300....etc until you reach (8,0) point on the graph. Graph a straight line down from starting point (0,400) on graph to (8,0). This is your answer subtract 50 from 400 until you reach 0. Starting point (0,400) and ending point (8,0), it's a straight line down ward..
Explanation: