A box is filled with solid balls. The total mass of the solid ball and the box is 12 kg. After removing (1/4) of the solid sphere from the box, the mass of the remaining solid sphere together with the box is 9.5 kg. What is the mass of this box in kilograms?
一个箱子里装满了实心球．实心球连箱子的质量总共为12千克．从箱中取出实心球的(1/4)后，剩下的实心球连箱子的质量总共为9.5千克．这个箱子的质量为多少千克？
<gadget id="calculator">12 - 9.5</gadget>
<output>2.5</output>

<gadget id="calculator">1 / 4</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>