The origin is at (0,0). When you move right or left, you change the x-coordinate, or the first coordinate. You moved right which is in the positive direction so now your coordinate is (4,0).
When you move up or down, you change the y-coordinate, or the second coordinate. You moved down which is in the negative direction so your final coordinate is (4, -3).
Interior angles and their exterior angles make a supplementary angle meaning they have a sum of 180°. Knowing this, we can make an equation to solve for x.
This is complicated because the scales on the x-axis and y-axis are not the same. Graph D has the correct y-intercepts and the correct slopes. The solution is x = 500, where the two lines intersect.