for (a), 2 ordered pairs (a,b) and (c,d) belong to the same equivalent class if

now, how do you prove that R is an equivalence relation?

i) aRa

ii) aRb then bRa

iii) if aRb and bRc, then aRc..

so, i believe, it is better that you post what you have done already so that we can check your work..