The number of apples is three times that of pears. If you eat 2 apples and 1 pear every day, after a few days, the pears are eaten up, and there are 7 apples left. How many original apples are there?
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，梨正好吃完，而苹果还剩下7个，原来的苹果有多少个？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">7 / (1/3)</gadget>
<output>21</output>

<result>21</result>