Testing Three Students

3 students are taking an examination of N subjects. Points are awarded according to the positions in each subject they took. The person who gets 1st will get the highest points, followed by 2nd and lastly 3rd. (So let 1st=X points, 2nd=Y points, 3rd=Z points.) Student B obtained X points in English. Student A obtained 22 points total. Students B and C obtained 9 points total each. How many subjects did they take in the examination, and what are the values of X, Y, Z?

Source: Reader Jimmy Chng Gim Hong, citing a Chinese puzzle book.

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