If the outer circumference of a steel pipe is 125.6 cm and the wall thickness of the pipe is 8 cm, what is the radius of the inner circle of the steel pipe in cm?
一根钢管的外圆周长是125.6厘米，管壁厚8厘米，钢管内圆半径是多少厘米．
<gadget id="calculator">125.6 / 3.14 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<result>12</result>