Two people each took 7 yuan to the bookstore to buy books. After buying a book each, the money left by one of them was exactly the same as the money the other person bought for the book. How much money do they have left?
两人各拿了7元钱到书店买书，各买了一本书后，其中一人剩下的钱正好与另一个人买书的钱一样多．他俩一共剩下多少元．
<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">14 - 7</gadget>
<output>7</output>

<result>7</result>