Let $R=\{(3,3),(6,6),(9,9),(12,12),(6,12),(3,9),(3,12),(3,6)\}$ be a relation on the set $A=\{3,6,9,12\}$. The relation is

$A=\{3,6,9,12\}$ and $(3,3),(6,6),(9,9),(12,12)\in R\Rightarrow R$ is reflexive

$(6,12)\in R$ but (12, 6) $\notin R\Rightarrow R$ is not symmetric

$(3,6)\in R,(6,12)\in R\Rightarrow (3,12)\in R$

$\therefore R$ is transitive