What are the coefficients that will balance the skeleton equation below? n + h ⟶ nh?

The coefficients are the whole numbers written before the substances to obey the Law of Conservation of Mass, or more specifically, the Law of Definite Proportions. You have to make sure that the number of each substance before and after the reaction must be the same. Thus, the given reaction is already balanced. The coefficient for each substance in the reaction is 1. When no coefficient is written, it is by default equal to 1.