There is a section of 3-meter-long money thread, which is used up (3/5) for the first time and (1/4) for the second time, how much is left?
有一段3米长的钱丝，第一次用去(3/5)，第二次用去(1/4)，还剩下几分之几？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (3/5) - (1/4)</gadget>
<output>3/20 = around 0.15</output>

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