pile of coal was originally planned to be burned for 20 days, but the actual saving was 0.4 tons per day. As a result, it was burned for 5 more days. How many tons were originally planned to be burned?
一堆煤，原计划烧20天，实际每天节约0.4吨，结果多烧了5天，原计划每烧多少吨？
<gadget id="calculator">20 * 0.4</gadget>
<output>8</output>

<gadget id="calculator">5 * 0.4</gadget>
<output>2</output>

<gadget id="calculator">8 + 2</gadget>
<output>10</output>

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

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

<gadget id="calculator">10 / 5</gadget>
<output>2</output>

<result>2</result>