SOLUTION: A shopkeeper bought some dozens of exercise books at ₦20.00 each. He found 13 of them torn, but he sells the rest at ₦32.00 each and makes a profit of ₦88.00. How many dozen

Let x be the number of dozens of exercise books bought.


Then the number of books bought was  12x.


The number of books sold is  (12x - 13). 


The money equation for the profit is easy to write.  It is


    (12x-13)*32 = 12x*20 + 88.



From this equation


    12x*32 - 12x*20  = 88 + 13*32,   or

    (12*32 - 12*20)x = 504

         144x        = 504

            x        =  = 3.5.


ANSWER.  3.5  dozens of books were bought.

         //  3.5 dozens is 12*3.5 = 42 books, so there is no reason to worry about the integer number of books.