A steel pipe, after (2/5) is used up, there are 12 meters left. How long is the steel pipe?
一根钢管，用去了(2/5)后还剩12米，这根钢管长多少．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">12 / (3/5)</gadget>
<output>20</output>

<result>20</result>