A pile of coal was originally planned to be burned for 20 days, but actually saved 4 tons per day, but it turned out to be burned for 5 more days. How many tons were originally planned to be burned per day?
一堆煤，原计划烧20天，实际每天节约4吨，结果多烧5天，原计划每天烧多少吨？
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">80 + 20</gadget>
<output>100</output>

<gadget id="calculator">5 - 20</gadget>
<output>-15</output>

<gadget id="calculator">20 + (-15)</gadget>
<output>5</output>

<gadget id="calculator">100 / 5</gadget>
<output>20</output>

<result>20</result>