A pile of coal is planned to be burned for 50 days a day, and 0.5 tons are burned every day. If 0.1 tons is saved every day, how many more days can it be burned? (Solve with ratio)
一堆煤，计划每天烧50天，每天烧0.5吨，如果每天节约0.1吨，可以多烧多少天？(用比例解)
<gadget id="calculator">50 * 0.5</gadget>
<output>25</output>

<gadget id="calculator">50 * 0.1</gadget>
<output>5</output>

<gadget id="calculator">5 - 25</gadget>
<output>-20</output>

<gadget id="calculator">25 + (-20)</gadget>
<output>5</output>

<gadget id="calculator">0.5 - 0.1</gadget>
<output>0.4</output>

<gadget id="calculator">5 / 0.4</gadget>
<output>12.5</output>

<result>12.5</result>