A box is full of solid balls, and the weight of the box is 12 kg. After taking out 25% of the solid balls from the box, the remaining solid balls together with the box weigh 9.5 kg. How much does the box weigh?
一个箱子里装满了实心球，连箱子共重12千克，从箱子中取出实心球的25%后，剩下的实心球连箱重9.5千克，问箱子重多少千克？
<gadget id="calculator">12 - 9.5</gadget>
<output>2.5</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2.5 / (1/4)</gadget>
<output>10</output>

<gadget id="calculator">12 - 10</gadget>
<output>2</output>

<result>2</result>