Given that, A={2,3,4,5,......,16,17,18} and (a,b)≈(c,d) ∴ Equivalence class of (3,2) is {(a,b)∈A×A=(a,b)R(c,d)} ={(a,b)∈A×A:2a=3b} ={(a,b)∈A×A:b=
2
3
a}{(a,
2
3
a):a∈A×A} ={(3,2),(6,4),(9,6),(12,8),(15,10),(18,12)} ∴ Number of ordered pairs of the equivalence class =6