2m long iron wire, cut off (9/10)m for the first time, and cut off (2/5)m for the second time, how much m is left?
一根长2m的铁丝，第一次剪去(9/10)m，第二次剪去(2/5)m，还剩多少m？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 - (9/10) - (2/5)</gadget>
<output>7/10 = around 0.7</output>

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