Xiaodong bought two sets of books with the same number of books in the bookstore. The first set was 12 yuan each, and the second set was 16 yuan each. The total cost was 84 yuan. How many books are there in each set? (column equation solution)
小冬在书店买了两套本数相同的图书，第一套每本12元，第二套每本16元，一共花了84元，每套图书各有多少本？(列方程解答)
<gadget id="calculator">12 + 16</gadget>
<output>28</output>

<gadget id="calculator">84 / 28</gadget>
<output>3</output>

<result>3</result>