Answer:
Place the ruler such that the edge is against the object. Parallax is a distortion of view because humans see through two sources, not just one. the farther the object is away from the ruler, the more that parallax can affect the situation.
Step-by-step explanation:
x = 4
2x/2 = 8/2
x =4
3
2 / (2/3) = 2 * 3/2 = 6/2 = 3