We have,
A = {a, b, c} and R = {(a, a), (b, c), (a, b)}
R can be a reflexive relation only when elements (b, b) and (c, c) are added to it
R can be a transitive relation only when the element (a, c) is added to it
So, the minmum number of ordered pairs to be added in R is 3.