A wire uses half of its total length for the first time, and 5 meters for the second time, leaving 20 meters left. How long is the wire originally?
一根电线第一次用去全长的一半，第二次又用去5米，还剩下20米，这根电线原来长多少米？
<gadget id="calculator">20 + 5</gadget>
<output>25</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">25 / (1/2)</gadget>
<output>50</output>

<result>50</result>