If unable to solve using Prover9, could you solve it without using it?

I. An equivalence relation (ER) on a set can be seen as a structure A, R), where A is a non-empty set, and R A A is a binary relation with the following properties 1. For every aEA: (a, a) ER (reflexivity) 2. For every a,DE A: (a, bjeR (b, a) R (symmetry)