I want to know the title, author and publisher of the most common
biology textbook used for teaching purposes in public high schools
within or near Philadelphia in the year 1975.

I need to purchase this textbook, so a complete answer to this
question should contain information about where it can be purchased.

Perhaps a retired teacher could help you.  Here is the link for
retirees of the Philadelphia Federation of Teachers:
http://www.pft.org/retirement/index.html

Otherwise: Researchers will ask if you have any  - the slightest - 
additional information about the book.