pile of coal, originally burned 0.8 tons per day, can be burned for 15 days. Later, the technology was improved to save 0.2 tons of coal per day. How many days can this batch of coal be burned now?
一堆煤，原来每天烧0.8吨，可以烧15天．后来改进技术每天节约用煤0.2吨，这批煤现在可以烧多少天？
<gadget id="calculator">0.8 - 0.2</gadget>
<output>0.6</output>

<gadget id="calculator">15 / 0.6</gadget>
<output>25</output>

<gadget id="calculator">0.8 * 25</gadget>
<output>20</output>

<result>20</result>