OpenStudy (anonymous):

How many arrangements of the 26 letters of the alphabet in which a occurs before b and c occurs before d?

7 years ago
OpenStudy (anonymous):

each pair does not have to be contiguous? so a, letter1, letter2, letter3, b is acceptable?

7 years ago
OpenStudy (anonymous):

see 'b' 'c' 'd' is the same letter. then, alphabet consist 23 letters and 'b' 'b' 'b' . and arrange!

7 years ago
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