Wang Li can earn 12 yuan by selling newspapers during the day, but spends 7 yuan every night. If he is penniless now, how many days will it take to earn 500 yuan.
王力每天白天卖报纸可以赚12元钱，但是每天晚上要花掉7元，如果他现在身无分文，那么要多少天才能赚够500元．
<gadget id="calculator">12 - 7</gadget>
<output>5</output>

<gadget id="calculator">500 / 5</gadget>
<output>100</output>

<gadget id="calculator">100 - 1</gadget>
<output>99</output>

<result>99</result>