There are two piles of coal, A and B. The weight of coal in pile A is three times that of pile B. If 80 tons of coal are transported from pile A to pile B, the quality of the two piles of coal is equal. How many tons of coal is there in pile B?
有甲乙两堆煤，甲堆煤的重量是乙堆煤的3倍，如果从甲堆运出80吨给乙堆，这时两堆煤的质量相等，原来乙堆有煤多少吨？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

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

<gadget id="calculator">80 * 1</gadget>
<output>80</output>

<result>80</result>