If the letters in the word "PSCEXAM" are rearranged according to the reverse English alphabetical order, how many letter(s) will remain in the same position after the rearrangement?

Let us write down the original positioning of the letters in the word "PSCEXAM":
$$\text{Original Position: }\left(\begin{array}{ccccccc}1& 2& 3& 4& 5& 6& 7\\ \text{P}& \text{S}& \text{C}& \text{E}& \text{X}& \text{A}& \text{M}\end{array}\right)$$

Now, let us arrange these letters in reverse English alphabetical order (from highest to lowest alphabetical rank: X, S, P, M, E, C, A):

$$\text{Rearranged Position: }\left(\begin{array}{ccccccc}1& 2& 3& 4& 5& 6& 7\\ \text{X}& \text{S}& \text{P}& \text{M}& \text{E}& \text{C}& \text{A}\end{array}\right)$$

Let us compare the elements side by side:

* Position 1: P vs X (Changed)
* Position 2: S vs S (Same)
* Position 3: C vs P (Changed)
* Position 4: E vs M (Changed)
* Position 5: X vs E (Changed)
* Position 6: A vs C (Changed)
* Position 7: M vs A (Changed)

Only $1$ letter, 'S', remains in the same position after rearrangement.