If (R) on (A={1,2,3}) is reflexive and symmetric and ((1,2)) and ((2,3)) are in (R), which pairs must be present to make it an equivalence relation?

Correct answer: ((1,3)) and ((3,1))

Step 1: Reflexivity gives self-pairs, and symmetry gives reverse pairs. Step 2: ((1,2)) and ((2,3)) require ((1,3)) by transitivity. Step 3: To keep symmetry, ((3,1)) is also needed.