188÷[ 1+ 8 13 ×( 1- 2 3 )],

= 188÷( 1+ 8 39 ),

= 188÷ 47 39 ,

= 156 (Ben);

Three classes donated books:

156×( 1+ 8 13 + 8 39 ),

= 156× 7 1 39 ,

=284 (Ben);

A: These three classes donated 284 books.

So the answer is: 284.