Exercise 2, there is a pile of yellow sand, and it needs to be transported 50 times by a big car, and 80 times if it is transported by a small car. Each big car transports 3 tons more than a small car. How many tons is this pile of yellow sand?
练习2，有一堆黄沙，用大汽车运需运50次，如果用小汽车运，要运80次．每辆大汽车比小汽车多运3吨，这堆黄沙有多少吨？
<gadget id="calculator">1 / 50</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">1 / 80</gadget>
<output>1/80 = around 0.0125</output>

<gadget id="calculator">(1/50) - (1/80)</gadget>
<output>3/400 = around 0.0075</output>

<gadget id="calculator">3 / (3/400)</gadget>
<output>400</output>

<result>400</result>