Why is x - y = 8 and y - x = c have many solution?

Arepresentative from plan 1 wants to use the graph below to sell health plans for his company. how might the graph be redrawn to emphasize the difference between the cost per doctor visit for each of the three plans? the scale on the y-axis could be changed to 0–100. the scale on the y-axis could be changed to 25–40. the interval of the y-axis could be changed to count by 5s. the interval of the y-axis could be changed to count by 20s.