Total number of equivalence relations defined in the set S={a,b,c} is:
5
3!
23
33
The smallest equivalence relation is the identify relation
R1={(a,a),(b,b)(c,c)}
Then two ordered pairs of two distinct elements can be added to give three more equivalence relations R2={(a,a),(b,b)(c,c)(a,b),(b,a)}
Similarly R3 and R4 .finally the largest equivalence relation i.e., the universal relation
R5={(a,a),(b,b)(c,c)(a,b),(b,a),(a,c),(c,a)(b,c)(c,b)}