Explanation:
To find the width, we have to find the distance between (-450, -300) and (450, -300) because those are the endpoints of the arch. Since the y-coordinates of the 2 points are equal, we just have to subtract their x values, which is 450 - (-450) = 900.
To find the width, we have to find the distance between (0,0) (the maximum) and (0, -300) (the lowest point). This is 0 - (-300) = 300. Hope this helps!