Party A and Party B each have several books. It is understood that the number of books owned by Party A accounts for three-sevenths of the total number of books. If Party B gives Party A fifteen books, the number of books for both of them is equal. How many books did Party A and Party B originally have? 15× 2 ÷ (1-2× 3/7) = 30 ÷1/7 = 210 (Ben) ...........

2 10/0× 3/7 = 90. .......................................................................................................................................................

2 10 -90 = 120 ................................................................... b has it.