A pile of coal is planned to burn 2 tons per day, which can be burned for 30 days, but actually saves 0.5 tons per day, how many days can it actually be burned?
一堆煤，计划每天烧2吨，可以烧30天，实际每天节约0.5吨，实际可以烧多少天？
<gadget id="calculator">2 * 30</gadget>
<output>60</output>

<gadget id="calculator">2 - 0.5</gadget>
<output>1.5</output>

<gadget id="calculator">60 / 1.5</gadget>
<output>40</output>

<result>40</result>