The "Fundamental Relation of Thermodynamics" says that in equilibrium: where T is temperature, S is entropy, U is internal energy, p is pressure, and V is volume. This describes how, in equilibrium, S depends on changes in U and V. Here are other derivatives to evaluate, always assuming equilibrium so you can use the Fundamental Relation. The answers should be simple formulas expressed in terms of the variables S, T, U, V, and p.