Assuming that A2:C7 contains the data, and E2:E4 contains Math,
Science, and Business, try...

F2, confirmed with CONTROL+SHIFT+ENTER, and copied down:

=SUM(IF(FREQUENCY(IF($C$2:$C$7=E2,MATCH("~"&$A$2:$ A$7&$B$2:$B$7,$A$2:$A$7
&$B$2:$B$7&"",0)),ROW($C$2:$C$7)-ROW($C$2)+1),1))

Hope this helps!

In article ,
Ert wrote:

I have a large spread sheet and I want to know the total number of classes
for an area. Classes with the same title but at different HS need to be
counted seperately. For Example:
School Class Area
John HS Algebra Math
John HS Geometry Math
John HS Genetics Science
Jane HS Genetics Science
Jane HS Accounting Business
Jane HS Accounting Business

Total Unique Math Classes = 2
Total Unique Science Classes = 2
Total Unique Business Classes = 1

Thanks in advance.