How many such pairs of letters are there in the given word which has/have as many letters between them in the word as they have in the English alphabet?
FIRST

Let's check the letters of the word FIRST forward and backward according to their alphabetical positions:
F (6), I (9), R (18), S (19), T (20)

Forward Direction:

1. RS: In the alphabet, there are 0 letters between R and S. In FIRST, there are 0 letters between R and S. (1st pair)
2. RT: In the alphabet, there is 1 letter (S) between R and T. In FIRST, there is 1 letter (S) between R and T. (2nd pair)
3. ST: In the alphabet, there are 0 letters between S and T. In FIRST, there are 0 letters between S and T. (3rd pair)

Backward Direction:

* T (20) $\to$ S, R, I, F (No matching pairs)
* S (19) $\to$ R, I, F (No matching pairs)
* R (18) $\to$ I, F (No matching pairs)

There are a total of 3 such pairs (RS, RT, ST).