A piece of iron with a volume of 60cm**3 is completely submerged in a cuboid container with a bottom area of 20cm**3, and the height of the water surface is 15cm. If the iron piece is taken out, what is the height of the water surface?
把一个体积为60cm**3的铁块完全浸没在底面积为20cm**3的长方体容器中，水面高度为15cm，如果把铁块捞出后，水面高是多少？
<gadget id="calculator">60 / 20</gadget>
<output>3</output>

<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<result>12</result>