There are two piles of coal, the first pile is 4 times the second pile. When the second pile of coal is transported 6.25 tons, the first pile of coal is 6 times that of the second pile of coal. How many tons is the second pile of coal?
有两堆煤，第一堆是第二堆的4倍．当第二堆煤运走6.25吨后，第一堆煤是第二堆煤的6倍．第二堆煤原有多少吨？
<gadget id="calculator">6 * 6.25</gadget>
<output>37.5</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">37.5 / 2</gadget>
<output>18.75</output>

<result>18.75</result>