30% of a rope is used up, how much is left?
一根绳子用去了30%，还剩多少．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<result>7/10 = around 0.7</result>