If you're storing the teacher's name in the Borrowing table... your
design is probably wrong.

That said: create a Query based on this table. Select the book's name
and teacher's name field. View the query's Properties, and set the
"Unique Values" property to true. This will give one record for each
book that the teacher borrowed (no matter how many times that book was
borrowed).

Now create ANOTHER query based on this query. Make it a Totals query
by clicking the Greek Sigma icon - it looks like a sideways W. Group
By the teacher's name and select the Book's Name field *twice*; Group
By one instance and Count the other.

                 John W. Vinson[MVP]

If I understand correctly, you have a report that is grouped by Teacher and
displays books in the detail section. You should be able to display either a
header or a footer section for the teacher and add a text box with a control
source of:
=Count(*)
To count the number of different teachers, add a text box to the teacher
group header:
   Name: txtCountTeach
   Control Source: =1
   Running Sum: Over All
   Visible: No
Then add a text box to your report footer:
   Control Source: =txtCountTeach