There are two piles of yellow sand on the construction site. The first pile weighs 6.4 tons, which is 0.8 tons more than twice that of the second pile. How many tons is the second pile of yellow sand?
工地上有两堆黄沙，第一堆重6.4吨，比第二堆的2倍多0.8吨，第二堆黄沙有多少吨？
<gadget id="calculator">6.4 - 0.8</gadget>
<output>5.6</output>

<gadget id="calculator">5.6 / 2</gadget>
<output>2.8</output>

<result>2.8</result>