Where is the transistivity in this equivalence relation The following set has been given: $A = \{1,2,3\}$, and the following relation on $A$ has been given: $S = \{(1,1),(2,1),(1,2),(2,2),(3,3)\}$. The answer says this is a valid equivalence relation. I can see how it is symmetric and reflexive, but I can't see how and why it is transistive. What am I not understanding?

Can you find two pairs $\langle a,b\rangle,\langle b,c\rangle\in S$ such that $\langle a,c\rangle\notin S$? 
If not then you can conclude that the relation is transitive.
