A piece of iron wire is 10m long, 25% of it is used for the first time, and (2/5)m is used for the second time, how many meters are left?
一段铁丝长10m，第一次用去了25%，第二次用去了(2/5)m，还剩下多少米？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">10 * (1/4)</gadget>
<output>5/2 = around 2.5</output>

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

<gadget id="calculator">10 - (5/2) - (2/5)</gadget>
<output>71/10 = around 7.1</output>

<result>71/10 = around 7.1</result>