The number of apples is three times that of pears. If you eat 2 apples and 1 pear every day, after a few days, there are still 7 apples left, and the pears have just been eaten. Do you know how many apples there were?
苹果的个数是梨的3倍，如果每天吃2个苹果1个梨，若干天后，苹果还剩下7个，梨刚好吃完，你知道原来有几个苹果吗？
<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">7 / 1</gadget>
<output>7</output>

<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<result>21</result>