Books are identified by an international standard book number (isbn), a 10-digit code x1x2â¦x10, assigned by the publisher.
these 10 digits consist of blocks identifying the language, the publisher, the number assigned to the book by its publishing company, and finally, a 1-digit check digit that is either a digit or the letter x (used to represent 10).
this check digit is selected so that â10i=1ixiâ¡0 mod 11 and is used to detect errors in individual digits and transposition of digits.

(a) the isbn for a book is 8â51â532734âq where q is the check digit. what is q?

(b) the isbn of another book is 5â707â15m25â8. find the digit m.