Relation R defined on the set of seven-bit strings by s1Rs2, provided that the first four bits of s1 and s2 coincide
(i) Show that R is an equivalence relation.
(iii) List one (1) member of each equivalence class.
Here coincide is synonymous with same as. As such almost all such relations are equivalence relations.
You post your efforts on showing the three required properties.
For the second part, there will be sixteen strings.