除数 is read as じょすう (josuu) and means divisor.
じょすう
josuu
ひじょすう
dividend
じょがい
exception
じょめい
striking off a name
のぞいて
except
じょきょ
removal
のぞく
to exclude
じょそう
weeding
じょせつ
snow removal
じょや
New Year's Eve
じょじつ
New Year's eve
じょかんさ
(immunological) desensitization
じもく
ceremony for appointing officials other than ministers (from the Heian period)