Which statement is correct?
Book(Kenneth Rosen's Discrete Mathematics) Definition :- There are n/d ways to do a task if it can be done using a procedure that can be carried out in n ways, and for every way w, exactly d of the n ways correspond to way w.
I think this statement is more accurate :- There are n/d ways to do a task if it can be done using a procedure that can be carried out in n ways, and exactly every **d of the n ways corresponds to the same sequence.**
P.S. - I have written the part in Bold (where I have doubt). Sorry for my bad English (English is not my native language)
Well, your wording can use a little more polish, but do you seem to grasp the idea.
The requirement is that every way among the $n$ belongs to an equivalence class of exactly $d$ corresponding ways.
That is, you can partition the $n$ ways into disjoint sets of corresponding ways, each of which contains exactly $d$ ways (so every way is in exactly one of these, with no remainders).
And such.