I feel like a better explanation is that the answer is 26. I assumed that you were asking for {x|x, as long as x is a letter of the alphabet}. The cardinal number is basically just the number of terms in the set (it has to be distinct).
W is letter number 23 in the alphabet.
'I' is the 9th letter in the alphabet.'M' is the 13th letter in the alphabet.? ? ?
The letter U is the 21st letter in the alphabet.
The letter "G" corresponds to the number 7 in the alphabet.
The letter J is the 10th letter in the English alphabet. It is the 11th in the Spanish alphabet.
23 is not in the alphabet. It is a number. The next number is 24. If you are asking what the 24th letter of the alphabet is, it's X.
The letter L is the 12th letter in the English alphabet.
The letter Y is the 25th letter in the English alphabet.
In the English alphabet, the letter "f" is the 6th letter.
The letter "L" is the 12th letter in the alphabet.
M is the thirteenth letter in the alphabet.
no number does begin with P...but the first cardinal number to use the letter P is Septillion