For a pile of coal, 12.85 tons are transported every day, and 19.6 tons remain after 4 days of transportation. How many tons was this pile of coal originally?
一堆煤，每天运走12.85吨，运了4天后还剩下19.6吨．这堆煤原来有多少吨？
<gadget id="calculator">12.85 * 4</gadget>
<output>51.4</output>

<gadget id="calculator">51.4 + 19.6</gadget>
<output>71</output>

<result>71</result>