Final answer:
Without additional context or a specific formula, it is not possible to provide an accurate value of n such that the ratio of Xn is 1:3.
Step-by-step explanation:
To find the value of n on the XY plane such that the ratio of X₍n is 1:3, we would generally need a specific formula or additional context which seems to be absent in the provided information. The question seems to be related to geometric or algebraic concepts, and without further context.
It may refer to a coordinate point (Xn, Yn) where Xn is one-third the value of Yn, or a situation where the x-coordinate is one unit and the y-coordinate is three units. Since we do not have enough information to provide a definitive answer to this question, we can only speculate on the potential meaning without additional details.