There are two piles of coal, pile A is 28 tons more than pile B. If another 4 tons are transported from pile B to pile A, at this time, the weight of coal in pile A is twice that of pile B. How many tons of coal is there in pile A?
有两堆煤，甲堆比乙堆多28吨．如果再从乙堆中运4吨到甲堆，这时，甲堆的煤重是乙堆的2倍．甲堆原有煤多少吨？
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">28 + 8</gadget>
<output>36</output>

<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">36 / 1</gadget>
<output>36</output>

<gadget id="calculator">36 * 2</gadget>
<output>72</output>

<gadget id="calculator">72 - 4</gadget>
<output>68</output>

<result>68</result>