A candle burns the full length (7/10) for the first time, and the remaining half for the first time. What fraction of the full length of the candle is left?
一根蜡烛第一次燃烧了全长的(7/10)，第一次燃烧了剩下的一半．这跟蜡烛还剩下全长的几分之几？
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

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

<gadget id="calculator">(3/10) * (1/2)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 - (7/10) - (3/20)</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>